Publications by authors named "Fenglei Jiang"

19 Publications

  • Page 1 of 1

Mitochondrial toxicity induced by a thiourea gold(i) complex: mitochondrial permeability transition and respiratory deficit.

Toxicol Res (Camb) 2018 Nov 30;7(6):1081-1090. Epub 2018 Aug 30.

State Key Laboratory of Virology & Key Laboratory of Analytical Chemistry for Biology and Medicine (MOE) College of Chemistry and Molecular Sciences , Wuhan University , Wuhan 430072 , P. R. China . Email: ; ; Tel: +8627-68753465.

Gold(i) complexes have been widely used as antibacterial and antitumor agents because of their excellent biological activities. However, there are few reports on the study of gold(i) complexes at the subcellular level. Herein, we investigated the toxicity of a gold(i) complex (,'-disubstituted cyclic thiourea ligand) - AuTuCl - to isolated mitochondria various methods. The results showed that AuTuCl induced mitochondrial swelling, elevated ROS generation and triggered collapse of the membrane potential, which indicated the induction of mitochondrial permeability transition (MPT). It also enhanced the permeability of H and K of the inner membrane and declined membrane fluidity, which might be the result of MPT. Moreover, AuTuCl impaired the mitochondrial respiratory chain and suppressed the activities of complexes II and IV in the respiratory chain. It also triggered the deficiency of ATP and the effusion of Cyt , which were strictly related to respiration and apoptosis. These results indicated that AuTuCl severely affected the structure and function of mitochondria. It was proposed that MPT and impairment of the respiratory chain were responsible for the mitotoxicity of AuTuCl, thus causing energy deficiency and even apoptosis. This conceivable mechanism can serve as a clue for better understanding of the toxicology of AuTuCl.
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http://dx.doi.org/10.1039/c8tx00169cDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6240812PMC
November 2018

Aglycone Polyether Nanchangmycin and Its Homologues Exhibit Apoptotic and Antiproliferative Activities against Cancer Stem Cells.

ACS Pharmacol Transl Sci 2018 Nov 12;1(2):84-95. Epub 2018 Oct 12.

Key Laboratory of Combinatorial Biosynthesis and Drug Discovery (Ministry of Education), School of Pharmaceutical Sciences, Wuhan University, Wuhan, 430071, China.

The potential of the polyether salinomycin as an inhibitory agent against cancer stem cells has attracted interest in this family of compounds. In this study, we found that the aglycone polyether nanchangmycin and its homologues show promising activities against breast cancer stem cells as well as 38 other different types of cancer cells by assays. We found that aglycone polyethers caused elevations in calcium levels, an accumulation of reactive oxygen species and mitochondrial inner membrane permeability to H and K, resulting in the release of cytochrome and apoptosis-inducing factor and the triggering of caspase-dependent apoptosis. Our analyses also indicate that aglycone polyethers are potent Wnt/β-catenin signaling inhibitors, blocking the Wnt pathway and resulting in reduced cell survival. Notably, the key autophagy-related proteins LC3A/B were also activated by aglycone polyether treatment. Furthermore, nanchangmycin showed inhibitory effects toward somatic tumors developed from MCF-7 paclitaxel-resistant breast cancer cells injected into BALB/c mice. Our study not only provides promising candidates for therapy against cancer stem cells but also provides the groundwork for identifying stronger therapeutic agents among the natural polyether compounds.
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http://dx.doi.org/10.1021/acsptsci.8b00007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7088892PMC
November 2018

Indium (III) induces isolated mitochondrial permeability transition by inhibiting proton influx and triggering oxidative stress.

J Inorg Biochem 2017 12 8;177:17-26. Epub 2017 Sep 8.

State Key Laboratory of Virology, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China; Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China. Electronic address:

While Indium's toxicity to organs is realized, its effects on mitochondria are still under investigation. Mitochondrial permeability transition (MPT) is widely accepted in mitochondrial dysfunction approaches and its importance in metal-induced mitochondrial degradation has been proposed. Since mitochondria are respiratory organelles, their interaction with free In is analyzed to access structural and functional changes. Spectral methods and multimode plate reader was used to detect mitochondrial swelling, membrane potential, membrane fluidity, and inner membrane permeability. Flow cytometry was employed to detect mitochondrial reactive oxygen species (ROS) generation and transmission electron microscopy to image mitochondria. And oxygen electrode was used to measure respiratory rate, microcalorimetry to monitor long-term real-time mitochondrial metabolism. In at a concentration up to 1mM induces mitochondrial swelling, membrane depolarization and inhibits the protons transportation. In-induced mitochondrial swelling and membrane depolarization is protected by MPT inhibitors and -SH protectors, but the influence on protons transportation is not protected. In addition, In is able to accelerate the ROS production and inhibit the electron transition and respiratory chain while it stimulates long-term metabolism. Our findings show that In induces MPT by inhibiting the proton channels located in the inner mitochondrial membrane and by stimulating mitochondrial oxidative stress.
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http://dx.doi.org/10.1016/j.jinorgbio.2017.08.012DOI Listing
December 2017

Rapid and Selective Detection of Pathogenic Bacteria in Bloodstream Infections with Aptamer-Based Recognition.

ACS Appl Mater Interfaces 2016 Aug 25;8(30):19371-8. Epub 2016 Jul 25.

Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University , Wuhan, P. R. China.

Sepsis and bacteremia are life-threatening clinical syndromes associated with significant patient morbidity and mortality. Rapid and sensitive detection of pathogenic bacteria is the key to improve patient survival rates. Herein, we have rationally constructed a simple aptamer-based capture platform to shorten the time needed for confirmation of bacterial bloodstream infection in clinical blood samples. This capture platform is made of a mesoporous TiO2-coated magnetic nanoparticle and is modified with target aptamer. It features excellent bacterial enrichment efficiency of about 80% even at low bacterial concentrations (10-2000 CFU mL(-1)). More importantly, the bacteria can be enriched within 2 h, and the time for bacterial identification is effectively shortened in comparison to the "gold standard" in clinical diagnosis of bloodstream infection. The aptamer-based capture platform may pave a way for the detection of biomarkers and find potential applications in disease diagnosis.
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http://dx.doi.org/10.1021/acsami.6b06671DOI Listing
August 2016

Comparison of interactions between human serum albumin and silver nanoparticles of different sizes using spectroscopic methods.

Luminescence 2015 Jun 8;30(4):397-404. Epub 2014 Aug 8.

State Key Laboratory of Virology & Key Laboratory of Analytical Chemistry for Biology and Medicine (MOE), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, People's Republic of China; Hubei Key Laboratory for Processing and Application of Catalytic Materials, Huanggang Normal University, Huanggang, 438000, People's Republic of China.

Three different sizes (15.9 ± 2.1 nm, 26.4 ± 3.2 nm and 39.8 ± 4.0 nm, respectively) of citrate-coated silver nanoparticles (SNPs) have been synthesized and characterized. The interactions of the synthesized SNPs with human serum albumin (HSA) at physiological pH have been systematically studied by UV-vis absorption spectroscopy, fluorescence spectroscopy, synchronous fluorescence spectroscopy, three-dimensional fluorescence spectroscopy and circular dichroism (CD) spectroscopy. The results indicate that the SNPs can bind to HSA with high affinity and quench the intrinsic fluorescence of HSA. The binding constants and quenching rate constants were calculated. The apparent association constants (Kapp ) values are 2.14 × 10(4) M(-1) for 15.9 nm SNP, 1.65 × 10(4) M(-1) for 26.4 nm SNP and 1.37 × 10(4) M(-1) for 39.8 nm SNP, respectively. The values of binding constant obtained from the fluorescence quenching data match well with that determined from the absorption spectral changes. These results suggest that the smaller SNPs have stronger interactions to HSA than the larger ones at the same concentrations. Synchronous fluorescence, three-dimensional fluorescence and CD spectroscopy studies show that the synthesized SNPs can induce slight conformational changes in HSA.
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http://dx.doi.org/10.1002/bio.2748DOI Listing
June 2015

Chiral effect at protein/graphene interface: a bioinspired perspective to understand amyloid formation.

J Am Chem Soc 2014 Jul 18;136(30):10736-42. Epub 2014 Jul 18.

School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology , 122 Luoshi Road, Wuhan 430070, People's Republic of China.

Protein misfolding to form amyloid aggregates is the main cause of neurodegenerative diseases. While it has been widely acknowledged that amyloid formation in vivo is highly associated with molecular surfaces, particularly biological membranes, how their intrinsic features, for example, chirality, influence this process still remains unclear. Here we use cysteine enantiomer modified graphene oxide (GO) as a model to show that surface chirality strongly influences this process. We report that R-cysteine modification suppresses the adsorption, nucleation, and fiber elongation processes of Aβ(1-40) and thus largely inhibits amyloid fibril formation on the surface, while S-modification promotes these processes. And surface chirality also greatly influences the conformational transition of Aβ(1-40) from α-helix to β-sheet. More interestingly, we find that this effect is highly related to the distance between chiral moieties and GO surface, and inserting a spacer group of about 1-2 nm between them prevents the adsorption of Aβ(1-40) oligomers, which eliminates the chiral effect. Detailed study stresses the crucial roles of GO surface. It brings novel insights for better understanding the amyloidosis process on surface from a biomimetic perspective.
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http://dx.doi.org/10.1021/ja5049626DOI Listing
July 2014

Exploiting the role of resveratrol in rat mitochondrial permeability transition.

J Membr Biol 2013 May 12;246(5):365-73. Epub 2013 Apr 12.

State Key Laboratory of Virology & Key Laboratory of Analytical Chemistry for Biology and Medicine, Ministry of Education, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, People's Republic of China.

Resveratrol (RSV), a natural polyphenolic antioxidant, has been considered an anticarcinogenic agent as it triggers tumor cell apoptosis through activation of the mitochondrial pathway. In our study, the effects of RSV on mitochondria, especially on the mitochondrial permeability transition (MPT) process, were investigated by multiple methods. We found that RSV induced a collapse of membrane potential and matrix swelling related to MPT. We further demonstrated that Ca²⁺ was necessary for this RSV-induced MPT opening. In addition, RSV induced the inner membrane permeabilization to H⁺ and K⁺, the depression of respiration and changes in membrane fluidity. The results suggested that RSV-induced MPT was accompanied by mitochondrial dysfunction. But the prohibition on lipid peroxidation and different effects of low- and high-dose RSV on membrane fluidity and respiration showed that the interaction of RSV and the mitochondria could not be the result of a single simple mechanism.
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http://dx.doi.org/10.1007/s00232-013-9540-0DOI Listing
May 2013

Rapid GAL gene switch of Saccharomyces cerevisiae depends on nuclear Gal3, not nucleocytoplasmic trafficking of Gal3 and Gal80.

Genetics 2011 Nov 2;189(3):825-36. Epub 2011 Sep 2.

Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA.

The yeast transcriptional activator Gal4 localizes to UAS(GAL) sites even in the absence of galactose but cannot activate transcription due to an association with the Gal80 protein. By 4 min after galactose addition, Gal4-activated gene transcription ensues. It is well established that this rapid induction arises through a galactose-triggered association between the Gal80 and Gal3 proteins that decreases the association of Gal80 and Gal4. How this happens mechanistically remains unclear. Strikingly different hypotheses prevail concerning the possible roles of nucleocytoplasmic distribution and trafficking of Gal3 and Gal80 and where in the cell the initial Gal3-Gal80 association occurs. Here we tested two conflicting hypotheses by evaluating the subcellular distribution and dynamics of Gal3 and Gal80 with reference to induction kinetics. We determined that the rates of nucleocytoplasmic trafficking for both Gal80 and Gal3 are slow relative to the rate of induction. We find that depletion of the nuclear pool of Gal3 slows the induction kinetics. Thus, nuclear Gal3 is critical for rapid induction. Fluorescence-recovery-after-photobleaching experiments provided data suggesting that the Gal80-Gal4 complex exhibits kinetic stability in the absence of galactose. Finally, we detect Gal3 at the UAS(GAL) only if Gal80 is covalently linked to the DNA-binding domain. Taken altogether, these new findings lead us to propose that a transient interaction of Gal3 with Gal4-associated Gal80 could explain the rapid response of this system. This notion could also explain earlier observations.
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http://dx.doi.org/10.1534/genetics.111.131839DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3213366PMC
November 2011

Mitochondria as target of quantum dots toxicity.

J Hazard Mater 2011 Oct 7;194:440-4. Epub 2011 Aug 7.

State Key Laboratory of Virology & Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China.

Quantum dots (QDs) hold great promise in many biological applications, with the persistence of safety concerns about the environment and human health. The present work investigated the potential toxicity of CdTe QDs on the function of mitochondria isolated from rat livers by examining mitochondrial respiration, swelling, and lipid peroxidation. We observed that QDs can significantly affect the mitochondrial membrane properties, bioenergetics and induce mitochondrial permeability transition (MPT). These results will help us learn more about QDs toxicity at subcellular (mitochondrial) level.
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http://dx.doi.org/10.1016/j.jhazmat.2011.07.113DOI Listing
October 2011

Microcalorimetric, spectroscopic and microscopic investigation on the toxic effects of CdTe quantum dots on Halobacterium halobium R1.

Nanotechnology 2010 Nov 29;21(47):475102. Epub 2010 Oct 29.

State Key Laboratory of Virology and Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, People's Republic of China.

The biological effect of CdTe quantum dots (QDs) on Halobacterium halobium R1 (H. halobium R1) growth was analyzed by a microcalorimetric technique. By using a TAM air eight channels microcalorimeter, the thermogenic curves of H. halobium R1 growth were obtained at 37 °C. To analyze the results, the maximum heat power (P(m)) and the growth rate constants (k) were determined, which showed that they were correlated to the concentration of QDs. The addition of quantum dots caused a gradual increase of P(m) and k at low concentrations of QDs, and a conspicuous decrease at high concentrations. For confirmation, the turbidity (OD(600)) and respiratory rate at different concentrations of QDs were studied. The morphology of H. halobium R1 cells both in the absence and presence of QDs was examined by transmission electron microscopy (TEM). The results of these studies were corroborated with ones derived from microcalorimetry. In this work, the mechanism of cytotoxicity of QDs was explored through fluorescence spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS) and microcalorimetry. It was clear that metabolic mechanism of H. halobium R1 growth was changed by the addition of QDs. To the best of our knowledge, the thermokinetics and toxicology of CdTe QDs against H. halobium R1 were obtained for the first time by microcalorimetry.
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http://dx.doi.org/10.1088/0957-4484/21/47/475102DOI Listing
November 2010

Gene activation by dissociation of an inhibitor from a transcriptional activation domain.

Mol Cell Biol 2009 Oct 3;29(20):5604-10. Epub 2009 Aug 3.

Department of Biochemistry, the Ohio State University, 484 West 12th Avenue, Columbus, OH 43210, USA.

Gal4 is a prototypical eukaryotic transcriptional activator whose recruitment function is inhibited in the absence of galactose by the Gal80 protein through masking of its transcriptional activation domain (AD). A long-standing nondissociation model posits that galactose-activated Gal3 interacts with Gal4-bound Gal80 at the promoter, yielding a tripartite Gal3-Gal80-Gal4 complex with altered Gal80-Gal4 conformation to enable Gal4 AD activity. Some recent data challenge this model, whereas other recent data support the model. To address this controversy, we imaged fluorescent-protein-tagged Gal80, Gal4, and Gal3 in live cells containing a novel GAL gene array. We find that Gal80 rapidly dissociates from Gal4 in response to galactose. Importantly, this dissociation is Gal3 dependent and concurrent with Gal4-activated GAL gene expression. When galactose-triggered dissociation is followed by galactose depletion, preexisting Gal80 reassociates with Gal4, indicating that sequestration of Gal80 by Gal3 contributes to the observed Gal80-Gal4 dissociation. Moreover, the ratio of nuclear Gal80 to cytoplasmic Gal80 decreases in response to Gal80-Gal3 interaction. Taken together, these and other results provide strong support for a GAL gene switch model wherein Gal80 rapidly dissociates from Gal4 through a mechanism that involves sequestration of Gal80 by galactose-activated Gal3.
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http://dx.doi.org/10.1128/MCB.00632-09DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2756894PMC
October 2009

Analysis of Nsdhl-deficient embryos reveals a role for Hedgehog signaling in early placental development.

Hum Mol Genet 2006 Nov 6;15(22):3293-305. Epub 2006 Oct 6.

Center for Molecular and Human Genetics, Columbus Children's Research Institute, Department of Pediatrics, The Ohio State University, Columbus, OH 43205, USA.

The X-linked Nsdhl gene encodes a sterol dehydrogenase involved in cholesterol biosynthesis. Mutations in this gene cause the male lethal phenotypes in human CHILD syndrome and bare patches (Bpa) mice. Affected male embryos for several mutant Nsdhl alleles die in mid-gestation with a thin and poorly vascularized placental labyrinth. The timing and specific abnormalities noted suggest a defect in one or more developmental signaling pathways as a possible mechanism. Here, we examined the possible involvement of the hedgehog signaling pathway in the placental pathology of Nsdhl mutants using a transgenic mouse line (Ptch1(tm1Mps)) that contains a lacZ reporter under the control of the promoter for Ptch1, the gene that encodes the major hedgehog receptor. We demonstrate expression of Ptch1 in allantoic mesoderm of the placenta from wild-type mid-gestation embryos. The evidence suggests that the signaling is induced by Indian hedgehog that is produced by distal (ectoplacental) visceral endoderm cells that migrate into the allantoic mesoderm before embryonic day 10.0. Using a ubiquitously expressed, X-linked lacZ transgene that undergoes normal X-inactivation, we demonstrate that the placental defects in Nsdhl/+ female embryos are non-cell autonomous. Further, affected placentas from mutant Nsdhl(Bpa-8H) male embryos demonstrate markedly decreased or no Ptch1-lacZ staining and no migration of Ihh expressing cells into the developing placenta. These data strongly implicate the hedgehog signaling pathway in the pathogenesis of the placental defects in NSDHL deficiency and provide evidence for a role for the hedgehog pathway in the development of a functional mammalian placenta.
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http://dx.doi.org/10.1093/hmg/ddl405DOI Listing
November 2006

Placental defects are associated with male lethality in bare patches and striated embryos deficient in the NAD(P)H Steroid Dehydrogenase-like (NSDHL) Enzyme.

Mol Genet Metab 2005 Jan;84(1):48-60

Center for Molecular and Human Genetics, Columbus Children's Research Institute, The Ohio State University, Columbus, OH 43205, USA.

NSDHL is a 3beta-hydroxysterol dehydrogenase that is involved in the removal of C-4 methyl groups in one of the later steps of cholesterol biosynthesis. Mutations in the Nsdhl gene are associated with the X-linked male lethal mouse mutations bare patches (Bpa) and striated (Str), as well as with most cases of human CHILD syndrome. To begin to examine the pathogenesis of these disorders, we have determined that affected male embryos for several Nsdhl alleles die in midgestation, between E10.5 and 13.5, while the majority of affected male embryos for the most severe allele, Nsdhl(Bpa1H), die prior to E9.5. Although no consistent anomalies were identified in affected male embryos themselves, the labyrinth layer of the fetal placenta was always thinner, with fewer fetal vessels and decreased proliferation of labyrinth trophoblast cells. X-inactivation is non-random in females in most lineages of the rodent placenta with preferential inactivation of the paternal X chromosome. For primary defects involving these extraembryonic lineages, heterozygous females with a mutant maternal X chromosome would be expected to have an identical placental phenotype to that found in affected male embryos. We hypothesize that abnormalities in cells of the allantoic mesoderm that undergo random X-inactivation and form the endothelial lining of the fetal vessels of the labyrinth are associated with the male lethality, perhaps through disruption of an as yet unidentified signaling pathway.
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http://dx.doi.org/10.1016/j.ymgme.2004.08.007DOI Listing
January 2005

Defining the regions of Escherichia coli YidC that contribute to activity.

J Biol Chem 2003 Dec 22;278(49):48965-72. Epub 2003 Sep 22.

Department of Chemistry, Ohio State University, Columbus, Ohio 43210, USA.

The YidC/Oxa1/Alb3 family of proteins catalyzes membrane protein insertion in bacteria, mitochondria, and chloroplasts. In this study, we investigated which regions of the bacterial YidC protein are important for its function in membrane protein biogenesis. In Escherichia coli, YidC spans the membrane six times, with a large 319-residue periplasmic domain following the first transmembrane domain. We found that this large periplasmic domain is not required for YidC function and that the residues in the exposed hydrophilic loops or C-terminal tail are not critical for YidC activity. Rather, the five C-terminal transmembrane segments that contain the three consensus sequences in the YidC/Oxa1/Alb3 family are important for its function. However, by systematically replacing all the residues in transmembrane segment (TM) 2, TM3, and TM6 with serine and by swapping TM4 and TM5 with unrelated transmembrane segments, we show that the precise sequence of these transmembrane regions is not essential for in vivo YidC activity. Single serine mutations in TM2, TM3, and TM6 impaired the membrane insertion of the Sec-independent procoat-leader peptidase protein. We propose that the five C-terminal transmembrane segments of YidC function as a platform for the translocating substrate protein to support its insertion into the membrane.
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http://dx.doi.org/10.1074/jbc.M307362200DOI Listing
December 2003

YidC is strictly required for membrane insertion of subunits a and c of the F(1)F(0)ATP synthase and SecE of the SecYEG translocase.

Biochemistry 2003 Sep;42(35):10537-44

Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA.

YidC was previously discovered to play a critical role for the insertion of the Sec-independent M13 procoat and Pf3 coat phage proteins into the Escherichia coli inner membrane. To determine whether there is an absolute requirement of YidC for membrane protein insertion of any endogenous E. coli proteins, we investigated a few representative membrane proteins. We found that membrane subunits of the F(0) sector of the F(1)F(0)ATP synthase and the SecE protein of the SecYEG translocase are highly dependent on YidC for membrane insertion, based on protease mapping and immunoblot analysis. We found that the SecE dependency on YidC for membrane insertion does not contradict the observation that depletion of YidC does not block SecYEG-dependent protein export at 37 degrees C. YidC depletion does not decrease the SecE level low enough to block export at 37 degrees C. In contrast, we found that protein export of OmpA is severely blocked at 25 degrees C when YidC is depleted, which may be due to the decreased SecE level, as a 50% decrease in the SecE levels drastically affects protein export at the cold temperature [Schatz, P. J., Bieker, K. L., Ottemann, K. M., Silhavy, T. J., and Beckwith, J. (1991) EMBO J. 10, 1749-57]. These studies reported here establish that physiological substrates of YidC include subunits of the ATP synthase and the SecYEG translocase, demonstrating that YidC plays a vital role for insertion of endogenous membrane proteins in bacteria.
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http://dx.doi.org/10.1021/bi034309hDOI Listing
September 2003

YidC, a newly defined evolutionarily conserved protein, mediates membrane protein assembly in bacteria.

Biol Chem 2002 Oct;383(10):1565-72

Department of Chemistry, The Ohio State University, Columbus, OH 43210-1185, USA.

Membranes contain proteins that catalyze a variety of reactions, which lead to the selective permeability of the membrane. For membrane proteins to function as receptors, transporters, channels, and ATPases, they must be targeted to their correct membrane and inserted into the lipid bilayer. Recently, a new membrane component called YidC was discovered that mediates the insertion of proteins into membranes in bacteria. YidC homologs also exist in mitochondria and chloroplasts. Depletion of YidC from the cell interferes with the insertion of membrane proteins that insert both dependent and independent of the SecYEG/SecDFYajC machinery. YidC directly interacts with membrane proteins during the membrane protein insertion process and assists in the folding of the hydrophobic regions into the membrane bilayer. The chloroplast and bacterial YidC homologs are truly functional homologs because the chloroplast homolog Alb3 functionally complements the bacterial YidC depletion strain. The role of YidC in the membrane insertion pathway will be reviewed.
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http://dx.doi.org/10.1515/BC.2002.176DOI Listing
October 2002

Functional analysis of the signal recognition particle in Escherichia coli by characterization of a temperature-sensitive ffh mutant.

J Bacteriol 2002 May;184(10):2642-53

Department of Microbiology, 207 Science I Building, Iowa State University, Ames, IA 50011, USA.

The Ffh protein of Escherichia coli is a 48-kDa polypeptide that is homologous to the SRP54 subunit of the eukaryotic signal recognition particle (SRP). Efforts to understand the function of Ffh in bacteria have depended largely on the use of E. coli strains that allow depletion of the wild-type gene product. As an alternative approach to studying Ffh, a temperature-sensitive ffh mutant was isolated. The ffh-10(Ts) mutation results in two amino acid changes in conserved regions of the Ffh protein, and characterization of the mutant revealed that the cells rapidly lose viability at the nonpermissive temperature of 42 degrees C as well as show reduced growth at the permissive temperature of 30 degrees C. While the ffh mutant is defective in insertion of inner membrane proteins, the export of proteins with cleavable signal sequences is not impaired. The mutant also shows elevated expression of heat shock proteins and accumulates insoluble proteins, especially at 42 degrees C. It was further observed that the temperature sensitivity of the ffh mutant was suppressed by overproduction of 4.5S RNA, the RNA component of the bacterial SRP, by stabilizing the thermolabile protein. Collectively, these results are consistent with a model in which Ffh is required only for localization of proteins integral to the cytoplasmic membrane and suggest new genetic approaches to the study of how the structure of the SRP contributes to its function.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC135024PMC
http://dx.doi.org/10.1128/jb.184.10.2642-2653.2002DOI Listing
May 2002

Chloroplast YidC homolog Albino3 can functionally complement the bacterial YidC depletion strain and promote membrane insertion of both bacterial and chloroplast thylakoid proteins.

J Biol Chem 2002 May 12;277(22):19281-8. Epub 2002 Mar 12.

Department of Chemistry, Molecular Cellular Developmental Biology Program and Protein Research Group, The Ohio State University, Columbus, Ohio 43210, USA.

A new component of the bacterial translocation machinery, YidC, has been identified that specializes in the integration of membrane proteins. YidC is homologous to the mitochondrial Oxa1p and the chloroplast Alb3, which functions in a novel pathway for the insertion of membrane proteins from the mitochondrial matrix and chloroplast stroma, respectively. We find that Alb3 can functionally complement the Escherichia coli YidC depletion strain and promote the membrane insertion of the M13 procoat and leader peptidase that were previously shown to depend on the bacterial YidC for membrane translocation. In addition, the chloroplast Alb3 that is expressed in bacteria is essential for the insertion of chloroplast cpSecE protein into the bacterial inner membrane. Surprisingly, Alb3 is not required for the insertion of cpSecE into the thylakoid membrane. These results underscore the importance of Oxa1p homologs for membrane protein insertion in bacteria and demonstrate that the requirement for Oxa1p homologs is different in the bacterial and thylakoid membrane systems.
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http://dx.doi.org/10.1074/jbc.M110857200DOI Listing
May 2002

Direct interaction of YidC with the Sec-independent Pf3 coat protein during its membrane protein insertion.

J Biol Chem 2002 Mar 20;277(10):7670-5. Epub 2001 Dec 20.

Department of Chemistry, Ohio State Biochemistry Program, and Protein Research Group, The Ohio State University, Columbus, Ohio 43210, USA.

YidC is a newly defined translocase component that mediates the insertion of proteins into the membrane bilayer. How YidC functions in the insertion process is not known. In this study, we report that the Sec-independent Pf3 coat protein requires the YidC protein specifically for the membrane translocation step. Using photocrosslinking techniques and ribosome-bound Pf3 coat derivatives with an extended carboxyl-terminal region, we found that the transmembrane region of the Pf3 coat protein physically interacts with YidC and the bacterial signal recognition particle Ffh component. We also find that in the insertion pathway, Pf3 coat interacts strongly with YidC only after its transmembrane segment is fully exposed outside the ribosome tunnel. Interaction between Pf3 coat and YidC occurs even in the absence of the proton motive force and with a Pf3 coat mutant that is defective in transmembrane insertion. Our study demonstrates that YidC can directly interact with a Sec-independent membrane protein, and the role of YidC is at the stage of folding the Pf3 protein into a transmembrane configuration.
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http://dx.doi.org/10.1074/jbc.M110644200DOI Listing
March 2002