Publications by authors named "Nikolaos Biris"

17 Publications

  • Page 1 of 1

MFN2 agonists reverse mitochondrial defects in preclinical models of Charcot-Marie-Tooth disease type 2A.

Science 2018 04;360(6386):336-341

Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, USA.

Mitofusins (MFNs) promote fusion-mediated mitochondrial content exchange and subcellular trafficking. Mutations in cause neurodegenerative Charcot-Marie-Tooth disease type 2A (CMT2A). We showed that MFN2 activity can be determined by Met and His interactions with Asp and Leu and controlled by PINK1 kinase-mediated phosphorylation of adjacent MFN2 Ser Small-molecule mimics of the peptide-peptide interface of MFN2 disrupted this interaction, allosterically activating MFN2 and promoting mitochondrial fusion. These first-in-class mitofusin agonists overcame dominant mitochondrial defects provoked in cultured neurons by CMT2A mutants MFN2 Arg→Gln and MFN2 Thr→Met, as demonstrated by amelioration of mitochondrial dysmotility, fragmentation, depolarization, and clumping. A mitofusin agonist normalized axonal mitochondrial trafficking within sciatic nerves of MFN2 Thr→Met mice, promising a therapeutic approach for CMT2A and other untreatable diseases of impaired neuronal mitochondrial dynamism and/or trafficking.
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http://dx.doi.org/10.1126/science.aao1785DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6109362PMC
April 2018

Correcting mitochondrial fusion by manipulating mitofusin conformations.

Nature 2016 12 24;540(7631):74-79. Epub 2016 Oct 24.

Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.

Mitochondria are dynamic organelles that exchange contents and undergo remodelling during cyclic fusion and fission. Genetic mutations in MFN2 (the gene encoding mitofusin 2) interrupt mitochondrial fusion and cause the untreatable neurodegenerative condition Charcot-Marie-Tooth disease type 2A (CMT2A). It has not yet been possible to directly modulate mitochondrial fusion, in part because the structural basis of mitofusin function is not completely understood. Here we show that mitofusins adopt either a fusion-constrained or a fusion-permissive molecular conformation, directed by specific intramolecular binding interactions, and demonstrate that mitofusin-dependent mitochondrial fusion can be regulated in mouse cells by targeting these conformational transitions. On the basis of this model, we engineered a cell-permeant minipeptide to destabilize the fusion-constrained conformation of mitofusin and promote the fusion-permissive conformation, reversing mitochondrial abnormalities in cultured fibroblasts and neurons that harbour CMT2A-associated genetic defects. The relationship between the conformational plasticity of mitofusin 2 and mitochondrial dynamism reveals a central mechanism that regulates mitochondrial fusion, the manipulation of which can correct mitochondrial pathology triggered by defective or imbalanced mitochondrial dynamics.
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http://dx.doi.org/10.1038/nature20156DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5315023PMC
December 2016

Identification of Neutrophil Exocytosis Inhibitors (Nexinhibs), Small Molecule Inhibitors of Neutrophil Exocytosis and Inflammation: DRUGGABILITY OF THE SMALL GTPase Rab27a.

J Biol Chem 2016 Dec 4;291(50):25965-25982. Epub 2016 Oct 4.

From the Departments of Molecular and Experimental Medicine and

Neutrophils constitute the first line of cellular defense in response to bacterial and fungal infections and rely on granular proteins to kill microorganisms, but uncontrolled secretion of neutrophil cargos is injurious to the host and should be closely regulated. Thus, increased plasma levels of neutrophil secretory proteins, including myeloperoxidase and elastase, are associated with tissue damage and are hallmarks of systemic inflammation. Here, we describe a novel high-throughput screening approach to identify small molecule inhibitors of the interaction between the small GTPase Rab27a and its effector JFC1, two central regulators of neutrophil exocytosis. Using this assay, we have identified small molecule inhibitors of Rab27a-JFC1 binding that were also active in cell-based neutrophil-specific exocytosis assays, demonstrating the druggability of Rab GTPases and their effectors. These compounds, named Nexinhibs (neutrophil exocytosis inhibitors), inhibit exocytosis of azurophilic granules in human neutrophils without affecting other important innate immune responses, including phagocytosis and neutrophil extracellular trap production. Furthermore, the compounds are reversible and potent inhibitors of the extracellular production of superoxide anion by preventing the up-regulation of the granule membrane-associated subunit of the NADPH oxidase at the plasma membrane. Nexinhibs also inhibit the up-regulation of activation signature molecules, including the adhesion molecules CD11b and CD66b. Importantly, by using a mouse model of endotoxin-induced systemic inflammation, we show that these inhibitors have significant activity in vivo manifested by decreased plasma levels of neutrophil secretory proteins and significantly decreased tissue infiltration by inflammatory neutrophils. Altogether, our data present the first neutrophil exocytosis-specific inhibitor with in vivo anti-inflammatory activity, supporting its potential use as an inhibitor of systemic inflammation.
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http://dx.doi.org/10.1074/jbc.M116.741884DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5207069PMC
December 2016

Synthetic Antibodies Inhibit Bcl-2-associated X Protein (BAX) through Blockade of the N-terminal Activation Site.

J Biol Chem 2016 Jan 12;291(1):89-102. Epub 2015 Nov 12.

From the Departments of Biochemistry and Medicine, Albert Einstein Cancer Center, Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, New York 10461,

The BCL-2 protein family plays a critical role in regulating cellular commitment to mitochondrial apoptosis. Pro-apoptotic Bcl-2-associated X protein (BAX) is an executioner protein of the BCL-2 family that represents the gateway to mitochondrial apoptosis. Following cellular stresses that induce apoptosis, cytosolic BAX is activated and translocates to the mitochondria, where it inserts into the mitochondrial outer membrane to form a toxic pore. How the BAX activation pathway proceeds and how this may be inhibited is not yet completely understood. Here we describe synthetic antibody fragments (Fabs) as structural and biochemical probes to investigate the potential mechanisms of BAX regulation. These synthetic Fabs bind with high affinity to BAX and inhibit its activation by the BH3-only protein tBID (truncated Bcl2 interacting protein) in assays using liposomal membranes. Inhibition of BAX by a representative Fab, 3G11, prevented mitochondrial translocation of BAX and BAX-mediated cytochrome c release. Using NMR and hydrogen-deuterium exchange mass spectrometry, we showed that 3G11 forms a stoichiometric and stable complex without inducing a significant conformational change on monomeric and inactive BAX. We identified that the Fab-binding site on BAX involves residues of helices α1/α6 and the α1-α2 loop. Therefore, the inhibitory binding surface of 3G11 overlaps with the N-terminal activation site of BAX, suggesting a novel mechanism of BAX inhibition through direct binding to the BAX N-terminal activation site. The synthetic Fabs reported here reveal, as probes, novel mechanistic insights into BAX inhibition and provide a blueprint for developing inhibitors of BAX activation.
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http://dx.doi.org/10.1074/jbc.M115.680918DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4697190PMC
January 2016

RING Dimerization Links Higher-Order Assembly of TRIM5α to Synthesis of K63-Linked Polyubiquitin.

Cell Rep 2015 Aug 23;12(5):788-97. Epub 2015 Jul 23.

Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX 78229, USA. Electronic address:

Members of the tripartite motif (TRIM) protein family of RING E3 ubiquitin (Ub) ligases promote innate immune responses by catalyzing synthesis of polyubiquitin chains linked through lysine 63 (K63). Here, we investigate the mechanism by which the TRIM5α retroviral restriction factor activates Ubc13, the K63-linkage-specific E2. Structural, biochemical, and functional characterization of the TRIM5α:Ubc13-Ub interactions reveals that activation of the Ubc13-Ub conjugate requires dimerization of the TRIM5α RING domain. Our data explain how higher-order oligomerization of TRIM5α, which is promoted by the interaction with the retroviral capsid, enhances the E3 Ub ligase activity of TRIM5α and contributes to its antiretroviral function. This E3 mechanism, in which RING dimerization is transient and depends on the interaction of the TRIM protein with the ligand, is likely to be conserved in many members of the TRIM family and may have evolved to facilitate recognition of repetitive epitope patterns associated with infection.
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http://dx.doi.org/10.1016/j.celrep.2015.06.072DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4526822PMC
August 2015

Rhesus monkey TRIM5α SPRY domain recognizes multiple epitopes that span several capsid monomers on the surface of the HIV-1 mature viral core.

J Mol Biol 2013 Dec 23;425(24):5032-44. Epub 2013 Jul 23.

Department of Biochemistry and Cancer Therapy and Research Center, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.

The restriction factor TRIM5α binds to the capsid protein of the retroviral core and blocks retroviral replication. The affinity of TRIM5α for the capsid is a major host tropism determinant of HIV and other primate immunodeficiency viruses, but the molecular interface involved in this host-pathogen interaction remains poorly characterized. Here we use NMR spectroscopy to investigate binding of the rhesus TRIM5α SPRY domain to a selection of HIV capsid constructs. The data are consistent with a model in which one SPRY domain interacts with more than one capsid monomer within the assembled retroviral core. The highly mobile SPRY v1 loop appears to span the gap between neighboring capsid hexamers making interhexamer contacts critical for restriction. The interaction interface is extensive, involves mobile loops and multiple epitopes, and lacks interaction hot spots. These properties, which may enhance resistance of TRIM5α to capsid mutations, result in relatively low affinity of the individual SPRY domains for the capsid, and the TRIM5α-mediated restriction depends on the avidity effect arising from the oligomerization of TRIM5α.
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http://dx.doi.org/10.1016/j.jmb.2013.07.025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4116666PMC
December 2013

Contribution of SUMO-interacting motifs and SUMOylation to the antiretroviral properties of TRIM5α.

Virology 2013 Jan 16;435(2):463-71. Epub 2012 Oct 16.

Department of Microbiology and Immunology, Albert Einstein College of Medicine Bronx, NY 10461, USA.

Recent findings suggested that the SUMO-interacting motifs (SIMs) present in the human TRIM5α (TRIM5α(hu)) protein play an important role in the ability of TRIM5α(hu) to restrict N-MLV. Here we explored the role of SIMs in the ability of rhesus TRIM5α (TRIM5α(rh)) to restrict HIV-1, and found that TRIM5α(rh) SIM mutants IL376KK (SIM1mut) and VI405KK (SIM2mut) completely lost their ability to block HIV-1 infection. Interestingly, these mutants also lost the recently described property of TRIM5α(rh) to shuttle into the nucleus. Analysis of these variants revealed that they are unable to interact with the HIV-1 core, which might explain the reason that these variants are not active against HIV-1. Furthermore, NMR titration experiments to assay the binding between the PRYSPRY domain of TRIM5α(rh) and the small ubiquitin-like modifier 1(SUMO-1) revealed no interaction. In addition, we examined the role of SUMOylation in restriction, and find out that inhibition of SUMOylation by the adenoviral protein Gam1 did not alter the retroviral restriction ability of TRIM5α. Overall, our results do not support a role for SIMs or SUMOylation in the antiviral properties of TRIM5α.
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http://dx.doi.org/10.1016/j.virol.2012.09.042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3534947PMC
January 2013

Structure of the rhesus monkey TRIM5α PRYSPRY domain, the HIV capsid recognition module.

Proc Natl Acad Sci U S A 2012 Aug 30;109(33):13278-83. Epub 2012 Jul 30.

Department of Biochemistry, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.

Tripartite motif protein TRIM5α blocks retroviral replication after cell entry, and species-specific differences in its activity are determined by sequence variations within the C-terminal B30.2/PRYSPRY domain. Here we report a high-resolution structure of a TRIM5α PRYSPRY domain, the PRYSPRY of the rhesus monkey TRIM5α that potently restricts HIV infection, and identify features involved in its interaction with the HIV capsid. The extensive capsid-binding interface maps on the structurally divergent face of the protein formed by hypervariable loop segments, confirming that TRIM5α evolution is largely determined by its binding specificity. Interactions with the capsid are mediated by flexible variable loops via a mechanism that parallels antigen recognition by IgM antibodies, a similarity that may help explain some of the unusual functional properties of TRIM5α. Distinctive features of this pathogen-recognition interface, such as structural plasticity conferred by the mobile v1 segment and interaction with multiple epitopes, may allow restriction of divergent retroviruses and increase resistance to capsid mutations.
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http://dx.doi.org/10.1073/pnas.1203536109DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3421187PMC
August 2012

Specificity and affinity of Lac repressor for the auxiliary operators O2 and O3 are explained by the structures of their protein-DNA complexes.

J Mol Biol 2009 Jul 18;390(3):478-89. Epub 2009 May 18.

Bijvoet Center for Biomolecular Research, Utrecht University, the Netherlands.

The structures of a dimeric mutant of the Lac repressor DNA-binding domain complexed with the auxiliary operators O2 and O3 have been determined using NMR spectroscopy and compared to the structures of the previously determined Lac-O1 and Lac-nonoperator complexes. Structural analysis of the Lac-O1 and Lac-O2 complexes shows highly similar structures with very similar numbers of specific and nonspecific contacts, in agreement with similar affinities for these two operators. The left monomer of the Lac repressor in the Lac-O3 complex retains most of these specific contacts. However, in the right half-site of the O3 operator, there is a significant loss of protein-DNA contacts, explaining the low affinity of the Lac repressor for the O3 operator. The binding mode in the right half-site resembles that of the nonspecific complex. In contrast to the Lac-nonoperator DNA complex where no hinge helices are formed, the stability of the hinge helices in the weak Lac-O3 complex is the same as in the Lac-O1 and Lac-O2 complexes, as judged from the results of hydrogen/deuterium experiments.
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http://dx.doi.org/10.1016/j.jmb.2009.05.022DOI Listing
July 2009

A TAF4-homology domain from the corepressor ETO is a docking platform for positive and negative regulators of transcription.

Nat Struct Mol Biol 2007 Jul 17;14(7):653-61. Epub 2007 Jun 17.

Laboratory of Molecular Biophysics, The Rockefeller University, 1230 York Avenue, New York, New York, 10021, USA.

The eight twenty-one protein, ETO, is implicated in 12%-15% of acute human leukemias as part of a gene fusion with RUNX1 (also called AML1). Of the four ETO domains related to Drosophila melanogaster Nervy, only two are required to induce spontaneous myeloid leukemia upon transplantation into the mouse. One of these domains is related in sequence to TAF4, a component of TFIID. The structure of this domain, ETO-TAFH, is similar to yeast Rpb4 and to Escherichia coli sigma(70); it is the first TAF-related protein with structural similarity to the multisubunit RNA polymerases. Overlapping surfaces of ETO-TAFH interact with an autonomous repression domain of the nuclear receptor corepressor N-CoR and with a conserved activation domain from the E-box family of transcription factors. Thus, ETO-TAFH acts as a structural platform that can interchange negative and positive coregulatory proteins to control transcription.
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http://dx.doi.org/10.1038/nsmb1258DOI Listing
July 2007

Disorder-order folding transitions underlie catalysis in the helicase motor of SecA.

Nat Struct Mol Biol 2006 Jul 18;13(7):594-602. Epub 2006 Jun 18.

Department of Chemistry, Rutgers University, Newark, New Jersey 07102, USA.

SecA is a helicase-like motor that couples ATP hydrolysis with the translocation of extracytoplasmic protein substrates. As in most helicases, this process is thought to occur through nucleotide-regulated rigid-body movement of the motor domains. NMR, thermodynamic and biochemical data show that SecA uses a novel mechanism wherein conserved regions lining the nucleotide cleft undergo cycles of disorder-order transitions while switching among functional catalytic states. The transitions are regulated by interdomain interactions mediated by crucial 'arginine finger' residues located on helicase motifs. Furthermore, we show that the nucleotide cleft allosterically communicates with the preprotein substrate-binding domain and the regulatory, membrane-inserting C domain, thereby allowing for the coupling of the ATPase cycle to the translocation activity. The intrinsic plasticity and functional disorder-order folding transitions coupled to ligand binding seem to provide a precise control of the catalytic activation process and simple regulation of allosteric mechanisms.
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http://dx.doi.org/10.1038/nsmb1108DOI Listing
July 2006

Influence of sequential oligopeptide carriers on the bioactive structure of conjugated epitopes: comparative study of the conformation of a Herpes simplex virus glycoprotein gD-1 epitope in the free and conjugated form, and protein "built-in" crystal structure.

Biopolymers 2006 ;84(4):383-99

Department of Chemistry, Section of Organic Chemistry and Biochemistry, University of Ioannina, 45110 Ioannina, Greece.

Synthetic carriers play an important role in immunogen presentation, due to their ability of inducing improved and specific responses to conjugated epitopes. Their influence on the bioactive conformation of the epitope, though admittedly crucial for relevant in vitro and in vivo applications, is difficult to evaluate, given the usual lack of information on the complex conformational features determined by the nature of the carrier and the mode of ligation. Using the Herpes simplex virus glycoprotein D-1 epitope (Leu(9)-Lys-Nle-Ala-Asp-Pro-Asn-Arg-Phe-Arg-Gly-Lys-Asp-Leu(22)) as a model, we have performed a detailed conformational analysis on the free epitope peptide in solution and on three constructs in which the epitope was conjugated to sequential oligopeptide carriers {Ac-[Lys-Aib-Gly](4)-OH (SOC(4))} (through either a thioether or an amide bond; Ac: acetyl) and polytuftsin oligomers {H-[Thr-Lys-Pro-Lys-Gly](4)-NH(2) (T20)}, (through a thioether bond). The analysis of the epitope conformation in the parent protein, in carrier-conjugated and free form, suggests that the beta-turn structure of the -Asp(13)-Pro-Asn-Arg(16)- segment is highly conserved and independent of the epitope form. However, small conformational variations were observed at the C-terminal part of the epitope, depending on the nature of the carrier.
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http://dx.doi.org/10.1002/bip.20486DOI Listing
August 2006

The relative orientation of the Arg and Asp side chains defined by a pseudodihedral angle as a key criterion for evaluating the structure-activity relationship of RGD peptides.

J Pept Sci 2004 Aug;10(8):494-509

Department of Chemistry, University of Ioannina, Ioannina 45110, Greece.

The ability of an integrin to distinguish between the RGD-containing extracellular matrix proteins is thought to be due partially to the variety of RGD conformations. Three criteria have been proposed for the evaluation of the structure-activity relationship of RGD-containing peptides. These include: (i) the distance between the charged centres, (ii) the distance between the Arg Cbeta and Asp Cbeta atoms, and (iii) the pseudo-dihedral angle defining the Arg and Asp side-chain orientation formed by the Arg Czeta, Arg Calpha, Asp Calpha and Asp Cgamma atoms. A comparative conformation-activity study was performed between linear RGD peptides and strongly constrained cyclic (S,S) -CDC- bearing compounds, which cover a wide range of inhibition potency of platelet aggregation. It is concluded that the fulfilment of the -45 degrees < or = pseudo-dihedral angle < or = +45 degrees criterion is a prerequisite for an RGD compound to exhibit inhibitory activity. Once this criterion is accomplished, the longer the distance between the charged centres and/or between the Arg and Asp Cbeta atoms, the higher is the biological activity. In addition, the stronger the ionic interaction between Arg and Asp charged side chains, the lower the anti-aggregatory activity.
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http://dx.doi.org/10.1002/psc.559DOI Listing
August 2004

Structure and flexibility adaptation in nonspecific and specific protein-DNA complexes.

Science 2004 Jul;305(5682):386-9

Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, Netherlands.

Interaction of regulatory DNA binding proteins with their target sites is usually preceded by binding to nonspecific DNA. This speeds up the search for the target site by several orders of magnitude. We report the solution structure and dynamics of the complex of a dimeric lac repressor DNA binding domain with nonspecific DNA. The same set of residues can switch roles from a purely electrostatic interaction with the DNA backbone in the nonspecific complex to a highly specific binding mode with the base pairs of the cognate operator sequence. The protein-DNA interface of the nonspecific complex is flexible on biologically relevant time scales that may assist in the rapid and efficient finding of the target site.
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http://dx.doi.org/10.1126/science.1097064DOI Listing
July 2004

Effect of synthetic peptides corresponding to residues 313-332 of the alphaIIb subunit on platelet activation and fibrinogen binding to alphaIIbbeta3.

Eur J Biochem 2004 Feb;271(4):855-62

Department of Chemistry Medical School, University of Ioannina, Greece.

The platelet integrin receptor alphaIIbbeta3 plays a critical role in thrombosis and haemostasis by mediating interactions between platelets and several ligands but primarily fibrinogen. It has been shown previously that the YMESRADR KLAEVGRVYLFL (313-332) sequence of the alphaIIb subunit plays an important role in platelet activation, fibrinogen binding and alphaIIbbeta3-mediated outside-in signalling. Furthermore, we recently showed that the 20-residue peptide (20-mer) alphaIIb 313-332, is a potent inhibitor of platelet aggregation and fibrinogen binding to alphaIIbbeta3, interacting with fibrinogen rather than the receptor. In an effort to determine the sequence and the minimum length required for the biological activity of the above 20-mer, we synthesized seven octapeptides, each overlapping by six residues, covering the entire sequence and studied their effect on platelet activation as well as fibrinogen binding to activated platelets. We show for the first time that octapeptides containing the RAD sequence are capable of inhibiting platelet aggregation and secretion as well as fibrinogen binding to the activated alphaIIbbeta3, possibly interacting with the ligand rather than the receptor. This suggests that the RAD sequence, common to all the inhibitory peptides, is critical for their biological activity. However, the presence of the YMES sequence, adjacent to RAD, significantly increases the peptide's biological potency. The development of such inhibitors derived from the 313-332 region of the alphaIIb subunit may be advantageous against the RGD-like antagonists as they could inhibit platelet activation without interacting with alphaIIbbeta3, thus failing to further induce alphaIIbbeta3-mediated outside-in signalling.
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http://dx.doi.org/10.1111/j.1432-1033.2004.03990.xDOI Listing
February 2004

Mapping the binding domains of the alpha(IIb) subunit. A study performed on the activated form of the platelet integrin alpha(IIb)beta(3).

Eur J Biochem 2003 Sep;270(18):3760-7

Department of Chemistry, University of Ioannina, Ioannina, Greece.

alpha(IIb)beta(3), a member of the integrin family of adhesive protein receptors, is the most abundant glycoprotein on platelet plasma-membranes and binds to adhesive proteins via the recognition of short amino acid sequences, for example the ubiquitous RGD motif. However, elucidation of the ligand-binding domains of the receptor remains controversial, mainly owing to the fact that integrins are conformationally labile during purification and storage. In this study, a detailed mapping of the extracellular region of the alpha(IIb) subunit is presented, using overlapping 20-peptides, in order to identify the binding sites of alpha(IIb) potentially involved in the platelet-aggregation event. Regions alpha(IIb) 313-332, alpha(IIb) 265-284 and alpha(IIb) 57-64 of alpha(IIb)beta(3) were identified as putative fibrinogen-binding domains because the corresponding peptides inhibited platelet aggregation and antagonized fibrinogen association, possibly by interacting with this ligand. The latter is further supported by the finding that the above peptides did not interfere with the binding of PAC-1 to the activated form of alpha(IIb)beta(3). Furthermore, alpha(IIb) 313-332 was found to bind to fibrinogen in a solid-phase binding assay. It should be emphasized that all the experiments in this study were carried out on activated platelets and consequently on the activated form of this integrin receptor. We hypothesize that RAD and RAE adhesive motifs, encompassed in alpha(IIb) 313-332, 265-284 and 57-64, are capable of recognizing complementary domains of fibrinogen, thus inhibiting the binding of this ligand to platelets.
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http://dx.doi.org/10.1046/j.1432-1033.2003.03762.xDOI Listing
September 2003

The Ac-RGD-NH2 peptide as a probe of slow conformational exchange of short linear peptides in DMSO.

Biopolymers 2003 May;69(1):72-86

Department of Chemistry, University of Ioannina, Greece.

According to general belief, the conformational information on short linear peptides in solution derived at ambient temperature from NMR spectrometry represents a population-weighted average over all members of an ensemble of rapidly interconverting conformations. Usually the search for discrete conformations is concentrated at low temperatures especially when sharp NMR resonances are detected at room temperature. Using the peptide Ac-RGD-NH(2) (Ac-Arg-Gly-Asp-NH(2), Ac: acetyl) as a model system and following a new approach, we have been able to demonstrate that short linear peptides can adopt discrete conformational states in DMSO-d(6) (DMSO: dimethylsulfoxide) which vary in a way critically dependent on the reconstitution conditions used before their dissolution in DMSO-d(6). The conformers are stabilized by intramolecular hydrogen bonds, which persist at high temperatures and undergo a very slow exchange with their extended structures in the NMR chemical shift time scale. The reported findings provide clear evidence for the occurrence of solvent-induced conformational exchange and point to DMSO as a valuable medium for folding studies of short linear peptides.
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http://dx.doi.org/10.1002/bip.10335DOI Listing
May 2003