Publications by authors named "Kenth Johansson"

17 Publications

  • Page 1 of 1

Patient-Tailored Levothyroxine Dosage with Pharmacokinetic/Pharmacodynamic Modeling: A Novel Approach After Total Thyroidectomy.

Thyroid 2021 Sep 22;31(9):1297-1304. Epub 2021 Jun 22.

Department of Sustainable Energy Technology, SINTEF Industry, Trondheim, Norway.

After seven decades of levothyroxine (LT4) replacement therapy, dosage adjustment still takes several months. We have developed a decision aid tool (DAT) that models LT4 pharmacometrics and enables patient-tailored dosage. The aim of this was to speed up dosage adjustments for patients after total thyroidectomy. The DAT computer program was developed with a group of 46 patients post-thyroidectomy, and it was then applied in a prospective randomized multicenter validation trial in 145 unselected patients admitted for total thyroidectomy for goiter, differentiated thyroid cancer, or thyrotoxicosis. The LT4 dosage was adjusted after only two weeks, with or without application of the DAT, which calculated individual free thyroxine (fT4) targets based on four repeated measurements of fT4 and thyrotropin (TSH) levels. The individual TSH target was either <0.1, 0.1-0.5, or 0.5-2.0 mIU/L, depending on the diagnosis. Initial postoperative LT4 dosage was determined according to clinical routine without using algorithms. A simplified DAT with a population-based fT4 target was used for thyrotoxic patients who often went into surgery after prolonged TSH suppression. Subsequent LT4 adjustments were carried out every six weeks until target TSH was achieved. When clinicians were guided by the DAT, 40% of patients with goiter and 59% of patients with cancer satisfied the narrow TSH targets eight weeks after surgery, as compared with only 0% and 19% of the controls, respectively. The TSH was within the normal range in 80% of DAT/goiter patients eight weeks after surgery as compared with 19% of controls. The DAT shortened the average dosage adjustment period by 58 days in the goiter group and 40 days in the cancer group. For thyrotoxic patients, application of the simplified DAT did not improve the dosage adjustment. Application of the DAT in combination with early postoperative TSH and fT4 monitoring offers a fast approach to LT4 dosage after total thyroidectomy for patients with goiter or differentiated thyroid cancer. Estimation of individual TSH-fT4 dynamics was crucial for the model to work, as removal of this feature in the applied model for thyrotoxic patients also removed the benefit of the DAT.
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http://dx.doi.org/10.1089/thy.2021.0125DOI Listing
September 2021

Optical coherence tomography for thyroid pathology: 3D analysis of tissue microstructure.

Biomed Opt Express 2020 Aug 9;11(8):4130-4149. Epub 2020 Jul 9.

Department of Biomedical Engineering, Linköping University, Linköping 581 85, Sweden.

To investigate the potential of optical coherence tomography (OCT) to distinguish between normal and pathologic thyroid tissue, 3D OCT images were acquired on thyroid samples from adult subjects (n=22) diagnosed with a variety of pathologies. The follicular structure was analyzed in terms of count, size, density and sphericity. Results showed that OCT images highly agreed with the corresponding histopatology and the calculated parameters were representative of the follicular structure variation. The analysis of OCT volumes provides quantitative information that could make automatic classification possible. Thus, OCT can be beneficial for intraoperative surgical guidance or in the pathology assessment routine.
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http://dx.doi.org/10.1364/BOE.394296DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7449746PMC
August 2020

Risk of Complications with Energy-Based Surgical Devices in Thyroid Surgery: A National Multicenter Register Study.

World J Surg 2016 Jan;40(1):117-23

Background: Energy-based surgical devices (EBD) combining cutting and coagulation are increasingly used in thyroid surgery. However, there is a lack of information about potential benefits and risk of complications outside controlled trials. The aims of this national multicenter register study were to describe the use of EDB, their potential effect on complication rates, and on operation time.

Materials And Methods: The Scandinavian Quality Register for Thyroid and Parathyroid surgery includes 35 surgical units in Sweden and covered 88% of the thyroid procedures performed during 2008–2009. The use of the EBD was specifically registered for 12 months, and 1297 patients were included. Surgically related complications and operation time were evaluated. The clamp-and-tie group (C-A-T) constituted the control group for comparison with procedures where EBD was used.

Results: The thyroid procedures performed included C-A-T (16.6%), bipolar electrosurgery (ES: 56.5%), electronic vessel sealing (EVS: 12.2%), and ultrasonic dissection (UD: 14.5%). Mean operative time was longer with EVS (p < 0.001) and shorter with UD (p < 0.05) than in the other groups. The bipolar ES group and the EVS group had higher incidence of calcium treatment at discharge and after 6 weeks than the UD group. No significant difference in nerve injury was found between the groups. There was a significant more frequent use of topical hemostatic agents in the EBD group compared to C-A-T.

Conclusion: In this national multicenter study, the use of UD shortened and EVS increased operating time. There was a higher risk of calcium treatment at discharge and after 6 weeks after use of EVS and bipolar ES than after UD use. There was a significant more frequent use of topical hemostatic agents in the EBD groups compared to C-A-T.
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http://dx.doi.org/10.1007/s00268-015-3270-7DOI Listing
January 2016

[Nuisances and inefficiency of surgical satellite patients. Structured record review and questionnaire study].

Lakartidningen 2012 Feb 15-21;109(7):338-41

Kirurgiska kliniken och patientsäkerhetsenheten, Universitetssjukhuset, Linköping.

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June 2012

Parafibromin and APC as screening markers for malignant potential in atypical parathyroid adenomas.

Endocr Pathol 2010 Sep;21(3):166-77

Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital Solna, CMM L8:01, 171 76 Stockholm, Sweden.

The identification of parathyroid carcinomas is based upon histopathological criteria in which an invasive growth pattern or distant metastasis is demonstrated. A dilemma arises when tumours present with atypical histopathological features but lack direct evidence of malignancy. Recently, reduced expression or loss of the tumour suppressor proteins parafibromin and adenomatous polyposis coli (APC) has been associated with parathyroid malignancy. We report results from APC and parafibromin expression analyses by immunohistochemistry and Western blot in five cases of atypical adenoma, a single case of carcinoma and 54 adenomas without atypical features. Complete loss of APC immunoreactivity and reduced expression of parafibromin was evident in two of the atypical adenomas and in the parathyroid carcinoma. By contrast, all adenomas displayed APC expression, including two cases with hyperparathyroidism 2 gene (HRPT2) mutations and loss of parafibromin expression. We conclude that loss of APC is a frequent molecular event in atypical adenomas and carcinomas, but not in adenomas. Following verification in an independent material, APC could become a valuable tool when assessing parathyroid tumours in the clinical setting. Furthermore, the molecular resemblance of atypical adenomas with carcinoma concerning parafibromin and APC expression indicates that atypical adenomas should be subjects to watchful follow-up.
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http://dx.doi.org/10.1007/s12022-010-9121-zDOI Listing
September 2010

Gastrointestinal microcirculation and cardiopulmonary function during experimentally increased intra-abdominal pressure.

Crit Care Med 2009 Jan;37(1):230-9

Center for Teaching and Research in Disaster Medicine and Traumatology, Linköping, Sweden.

Objectives: The aim of this study was to assess gastric, intestinal, and renal cortex microcirculation parallel with central hemodynamics and respiratory function during stepwise increase of intra-abdominal pressure (IAP).

Design: Prospective, controlled animal study.

Setting: Research laboratory, University Hospital.

Subjects: Twenty-six anesthetized and mechanically ventilated pigs.

Interventions: Following baseline registrations, CO2 peritoneum was inflated (n = 20) and IAP increased stepwise by 10 mm Hg at 10 mins intervals up to 50 mm Hg and subsequently exsufflated. Control animals (n = 6) were not insufflated with CO2.

Measurements And Main Results: The microcirculation of gastric mucosa, small bowel mucosa, small bowel seromuscular layer, colon mucosa, colon seromuscular layer, and renal cortex were selectively studied at all pressure levels and after exsufflation using a four-channel laser Doppler flowmeter (Periflex 5000, Perimed). Central hemodynamic and respiratory function data were registered at each level and after exsufflation. Cardiac output decreased significantly at IAP levels above 10 mm Hg. The microcirculation of gastric mucosa, renal cortex and the seromuscular layer of small bowel and colon was significantly reduced with each increase of IAP. The microcirculation of the small bowel mucosa and colon mucosa was significantly less affected compared with the serosa (p < 0.01).

Conclusions: Our animal model of low and high IAP by intraperitoneal CO2-insufflation worked well for studies of microcirculation, hemodynamics, and pulmonary function. During stepwise increases of pressure there were marked effects on global hemodynamics, respiratory function, and microcirculation. The results indicate that intestinal mucosal flow, especially small bowel mucosal flow, although reduced, seems better preserved in response to intra-abdominal hypertension caused by CO2-insufflation than other intra-abdominal microvascular beds.
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http://dx.doi.org/10.1097/CCM.0b013e318192ff51DOI Listing
January 2009

Results from the International Conference of Experts on Intra-abdominal Hypertension and Abdominal Compartment Syndrome. I. Definitions.

Intensive Care Med 2006 Nov 12;32(11):1722-32. Epub 2006 Sep 12.

Department of Intensive Care, Ziekenhuis Netwerk Antwerpen, Campus Stuivenberg, Lange Beeldekensstraat 267, 2060, Antwerpen 6, Belgium.

Objective: Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) have been increasingly recognized in the critically ill over the past decade. The variety of definitions proposed has led to confusion and difficulty in comparing one study to another.

Design: An international consensus group of critical care specialists convened at the second World Congress on Abdominal Compartment Syndrome to standardize definitions for IAH and ACS based upon the current understanding of the pathophysiology surrounding these two syndromes.

Methods: Prior to the conference the authors developed a blueprint for the various definitions, which was further refined both during and after the conference. The present article serves as the final report of the 2004 International ACS Consensus Definitions Conference and is endorsed by the World Society of Abdominal Compartment Syndrome (WSACS).

Results: IAH is redefined as an intra-abdominal pressure (IAP) at or above 12 mmHg. ACS is redefined as an IAP above 20 mmHg with evidence of organ dysfunction/failure. ACS is further classified as either primary, secondary, or recurrent based upon the duration and cause of the IAH-induced organ failure. Standards for IAP monitoring are set forth to facilitate accuracy of IAP measurements from patient to patient.

Conclusions: State-of-the-art definitions for IAH and ACS are proposed based upon current medical evidence as well as expert opinion. The WSACS recommends that these definitions be used for future clinical and basic science research. Specific guidelines and recommendations for clinical management of patients with IAH/ACS are published in a separate review.
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http://dx.doi.org/10.1007/s00134-006-0349-5DOI Listing
November 2006

Structural Basis of Redox Signaling in Photosynthesis: Structure and Function of Ferredoxin:thioredoxin Reductase and Target Enzymes.

Photosynth Res 2004 ;79(3):233-48

Integrated Department of Immunology, Howard Hughes Medical Institute, National Jewish Medical and Research Center & University of Colorado Health Sciences Center, 1400 Jackson St., K404, Denver, CO, 80206, USA.

The role of the ferredoxin:thioredoxin system in the reversible light activation of chloroplast enzymes by thiol-disulfide interchange with thioredoxins is now well established. Recent fruitful collaboration between biochemists and structural biologists, reflected by the shared authorship of the paper, allowed to solve the structures of all of the components of the system, including several target enzymes, thus providing a structural basis for the elucidation of the activation mechanism at a molecular level. In the present Review, these structural data are analyzed in conjunction with the information that was obtained previously through biochemical and site-directed mutagenesis approaches. The unique 4Fe-4S cluster enzyme ferredoxin:thioredoxin reductase (FTR) uses photosynthetically reduced ferredoxin as an electron donor to reduce the disulfide bridge of different thioredoxin isoforms. Thioredoxins in turn reduce regulatory disulfides of various target enzymes. This process triggers conformational changes on these enzymes, allowing them to reach optimal activity. No common activation mechanism can be put forward for these enzymes, as every thioredoxin-regulated protein undergoes specific structural modifications. It is thus important to solve the structures of the individual target enzymes in order to fully understand the molecular mechanism of the redox regulation of each of them.
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http://dx.doi.org/10.1023/B:PRES.0000017194.34167.6dDOI Listing
January 2004

Crystal structure and reactivity of YbdL from Escherichia coli identify a methionine aminotransferase function.

FEBS Lett 2004 Jul;571(1-3):141-6

Architecture et Fonction des Macromolécules Biologiques, UMR 6098, CNRS and Universités d'Aix-Marseille I and II, 31 chemin J. Aiguier, F-13402 Marseille Cedex 20, France.

The ybdL gene of Escherichia coli codes for a protein of unknown function. Sequence analysis showed moderate homology to several vitamin B(6) dependent enzymes, suggesting that it may bind pyridoxal-5'-phosphate. The structure analysis of YbdL to 2.35 A resolution by protein crystallography verifies that it is a PLP dependent enzyme of fold type I, the typical aspartate aminotransferase fold. The active site contains a bound pyridoxal-5'-phosphate, covalently attached to the conserved active site lysine residue Lys236. The pattern of conserved amino acids in the putative substrate binding pocket of the enzyme reveals that it is most closely related to a hyperthermophilic aromatic residue aminotransferase from the archeon Pyrococcus horikoshii. Activity tests with 10 amino acids as amino-donors reveal, however, a preference for Met, followed by His and Phe, results which can be rationalized by modelization studies.
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http://dx.doi.org/10.1016/j.febslet.2004.06.075DOI Listing
July 2004

The C-terminal domain of measles virus nucleoprotein belongs to the class of intrinsically disordered proteins that fold upon binding to their physiological partner.

Virus Res 2004 Feb;99(2):157-67

Architecture et Fonction des Macromolécules Biologiques, UMR 6098 CNRS et Université Aix-Marseille I et II, ESIL, Campus de Luminy, Cedex 09 13288, Marseille, France.

The nucleoprotein of measles virus consists of an N-terminal domain, N(CORE) (aa 1-400), resistant to proteolysis, and a C-terminal domain, N(TAIL) (aa 401-525), hypersensitive to proteolysis and not visible by electron microscopy. Using two complementary computational approaches, we predict that N(TAIL) belongs to the class of natively unfolded proteins. Using different biochemical and biophysical approaches, we show that N(TAIL) is indeed unstructured in solution. In particular, the spectroscopic and hydrodynamic properties of N(TAIL) indicate that this protein domain belongs to the premolten globule subfamily within the class of intrinsically disordered proteins. The isolated N(TAIL) domain was shown to be able to bind to its physiological partner, the phosphoprotein (P), and to undergo an induced folding upon binding to the C-terminal moiety of P [J. Biol. Chem. 278 (2003) 18638]. Using a computational analysis, we have identified within N(TAIL) a putative alpha-helical molecular recognition element (alpha-MoRE, aa 488-499), which could be involved in binding to P via induced folding. We report the bacterial expression and purification of a truncated form of N(TAIL) (N(TAIL2), aa 401-488) devoid of the alpha-MoRE. We show that N(TAIL2) has lost the ability to bind to P, thus supporting the hypothesis that the alpha-MoRE may play a role in binding to P. We have further analyzed the alpha-helical propensities of N(TAIL2) and N(TAIL) using circular dichroism in the presence of 2,2,2-trifluoroethanol. We show that N(TAIL2) has a lower alpha-helical potential compared to N(TAIL), thus suggesting that the alpha-MoRE may be indeed involved in the induced folding of N(TAIL).
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http://dx.doi.org/10.1016/j.virusres.2003.11.007DOI Listing
February 2004

Crystal structure of the measles virus phosphoprotein domain responsible for the induced folding of the C-terminal domain of the nucleoprotein.

J Biol Chem 2003 Nov 27;278(45):44567-73. Epub 2003 Aug 27.

Architecture et Fonction des Macromolécules Biologiques, UMR 6098 CNRS et Université Aix-Marseille, 13288 Marseille 09, France.

Measles virus is a negative-sense, single-stranded RNA virus belonging to the Mononegavirales order which comprises several human pathogens such as Ebola, Nipah, and Hendra viruses. The phosphoprotein of measles virus is a modular protein consisting of an intrinsically disordered N-terminal domain (Karlin, D., Longhi, S., Receveur, V., and Canard, B. (2002) Virology 296, 251-262) and of a C-terminal moiety (PCT) composed of alternating disordered and globular regions. We report the crystal structure of the extreme C-terminal domain (XD) of measles virus phosphoprotein (aa 459-507) at 1.8 A resolution. We have previously reported that the C-terminal domain of measles virus nucleoprotein, NTAIL, is intrinsically unstructured and undergoes induced folding in the presence of PCT (Longhi, S., Receveur-Brechot, V., Karlin, D., Johansson, K., Darbon, H., Bhella, D., Yeo, R., Finet, S., and Canard, B. (2003) J. Biol. Chem. 278, 18638-18648). Using far-UV circular dichroism, we show that within PCT, XD is the region responsible for the induced folding of NTAIL. The crystal structure of XD consists of three helices, arranged in an anti-parallel triple-helix bundle. The surface of XD formed between helices alpha2 and alpha3 displays a long hydrophobic cleft that might provide a complementary hydrophobic surface to embed and promote folding of the predicted alpha-helix of NTAIL. We present a tentative model of the interaction between XD and NTAIL. These results, beyond presenting the first measles virus protein structure, shed light both on the function of the phosphoprotein at the molecular level and on the process of induced folding.
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http://dx.doi.org/10.1074/jbc.M308745200DOI Listing
November 2003

Structural basis for feedback inhibition of the deoxyribonucleoside salvage pathway: studies of the Drosophila deoxyribonucleoside kinase.

Biochemistry 2003 May;42(19):5706-12

Department of Molecular Biology, Swedish University of Agricultural Sciences, Box 590, Biomedical Center, S-751 24 Uppsala, Sweden.

Deoxyribonucleoside kinases are feedback inhibited by the final products of the salvage pathway, the deoxyribonucleoside triphosphates. In the present study, the mechanism of feedback inhibition is presented based on the crystal structure of a complex between the fruit fly deoxyribonucleoside kinase and its feedback inhibitor deoxythymidine triphosphate. The inhibitor was found to be bound as a bisubstrate inhibitor with its nucleoside part in the nucleoside binding site and with its phosphate groups partially occupying the phosphate donor site. The overall structure of the enzyme--inhibitor complex is very similar to the enzyme--substrate complexes with deoxythymidine and deoxycytidine, except for a conformational change within a region otherwise directly involved in catalysis. This conformational change involves a magnesium ion, which is coordinated in the inhibitor complex to the phosphates and to the primary base, Glu52, that normally is positioned close to the 5'-OH of the substrate deoxyribose.
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http://dx.doi.org/10.1021/bi0340043DOI Listing
May 2003

The C-terminal domain of the measles virus nucleoprotein is intrinsically disordered and folds upon binding to the C-terminal moiety of the phosphoprotein.

J Biol Chem 2003 May 5;278(20):18638-48. Epub 2003 Mar 5.

Architecture et Fonction des Macromolécules Biologiques, UMR 6098 CNRS et Université Aix-Marseille I et II, ESIL, Campus de Luminy, 13288 Marseille Cedex 09, France.

The nucleoprotein of measles virus consists of an N-terminal moiety, N(CORE), resistant to proteolysis and a C-terminal moiety, N(TAIL), hypersensitive to proteolysis and not visible as a distinct domain by electron microscopy. We report the bacterial expression, purification, and characterization of measles virus N(TAIL). Using nuclear magnetic resonance, circular dichroism, gel filtration, dynamic light scattering, and small angle x-ray scattering, we show that N(TAIL) is not structured in solution. Its sequence and spectroscopic and hydrodynamic properties indicate that N(TAIL) belongs to the premolten globule subfamily within the class of intrinsically disordered proteins. The same epitopes are exposed in N(TAIL) and within the nucleoprotein, which rules out dramatic conformational changes in the isolated N(TAIL) domain compared with the full-length nucleoprotein. Most unstructured proteins undergo some degree of folding upon binding to their partners, a process termed "induced folding." We show that N(TAIL) is able to bind its physiological partner, the phosphoprotein, and that it undergoes such an unstructured-to-structured transition upon binding to the C-terminal moiety of the phosphoprotein. The presence of flexible regions at the surface of the viral nucleocapsid would enable plastic interactions with several partners, whereas the gain of structure arising from induced folding would lead to modulation of these interactions. These results contribute to the study of the emerging field of natively unfolded proteins.
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http://dx.doi.org/10.1074/jbc.M300518200DOI Listing
May 2003

Tetrameric NAD-dependent alcohol dehydrogenase.

Chem Biol Interact 2003 Feb;143-144:239-45

Department of Molecular Biology, Swedish University of Agricultural Sciences, S-751 24, Uppsala, Sweden.

Three-dimensional structures of the ethanol-induced, tetrameric alcohol dehydrogenase from Escherichia coli have recently been determined in the absence and presence of NAD. The structure of the E. coli enzyme is similar to those of the dimeric mammalian alcohol dehydrogenases, but it has a deletion of 21 residues located at the surface of the catalytic domain. The catalytic zinc ions have two different types of coordination, which are also observed in the class III dimeric mammalian alcohol dehydrogenase. Comparison of the structures provide new insights into the relationship between tetrameric and dimeric alcohol dehydrogenases and provide a link to the structure of the tetrameric yeast alcohol dehydrogenase.
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http://dx.doi.org/10.1016/s0009-2797(02)00222-3DOI Listing
February 2003

Structural basis for thermophilic protein stability: structures of thermophilic and mesophilic malate dehydrogenases.

J Mol Biol 2002 May;318(3):707-21

Department of Chemistry, University of Oslo, Box 1033, Blindern, N-0316 Oslo, Norway.

The three-dimensional structure of four malate dehydrogenases (MDH) from thermophilic and mesophilic phototropic bacteria have been determined by X-ray crystallography and the corresponding structures compared. In contrast to the dimeric quaternary structure of most MDHs, these MDHs are tetramers and are structurally related to tetrameric malate dehydrogenases from Archaea and to lactate dehydrogenases. The tetramers are dimers of dimers, where the structures of each subunit and the dimers are similar to the dimeric malate dehydrogenases. The difference in optimal growth temperature of the corresponding organisms is relatively small, ranging from 32 to 55 degrees C. Nevertheless, on the basis of the four crystal structures, a number of factors that are likely to contribute to the relative thermostability in the present series have been identified. It appears from the results obtained, that the difference in thermostability between MDH from the mesophilic Chlorobium vibrioforme on one hand and from the moderate thermophile Chlorobium tepidum on the other hand is mainly due to the presence of polar residues that form additional hydrogen bonds within each subunit. Furthermore, for the even more thermostable Chloroflexus aurantiacus MDH, the use of charged residues to form additional ionic interactions across the dimer-dimer interface is favored. This enzyme has a favorable intercalation of His-Trp as well as additional aromatic contacts at the monomer-monomer interface in each dimer. A structural alignment of tetrameric and dimeric prokaryotic MDHs reveal that structural elements that differ among dimeric and tetrameric MDHs are located in a few loop regions.
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http://dx.doi.org/10.1016/S0022-2836(02)00050-5DOI Listing
May 2002

Crystal structure of plant pectin methylesterase.

FEBS Lett 2002 Mar;514(2-3):243-9

Department of Molecular Biology, Swedish University of Agricultural Sciences, S-751 24 Uppsala, Sweden.

Pectin is a principal component in the primary cell wall of plants. During cell development, pectin is modified by pectin methylesterases to give different properties to the cell wall. This report describes the first crystal structure of a plant pectin methylesterase. The beta-helical structure embodies a central cleft, lined by several aromatic residues, that has been deduced to be suitable for pectin binding. The active site is found at the center of this cleft where Asp157 is suggested to act as the nucleophile, Asp136 as an acid/base and Gln113/Gln135 to form an anion hole to stabilize the transition state.
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http://dx.doi.org/10.1016/s0014-5793(02)02372-4DOI Listing
March 2002

A few amino acid substitutions can convert deoxyribonucleoside kinase specificity from pyrimidines to purines.

EMBO J 2002 Apr;21(7):1873-80

Section of Molecular Microbiology, BioCentrum-DTU, Building 301, Technical University of Denmark, DK-2800 Lyngby, Denmark.

In mammals, the four native deoxyribonucleosides are phosphorylated to the corresponding monophosphates by four deoxyribonucleoside kinases, which have specialized substrate specificities. These four enzymes are likely to originate from a common progenitor kinase. Insects appear to have only one multisubstrate deoxyribonucleoside kinase (dNK, EC 2.7.1.145), which prefers pyrimidine nucleosides, but can also phosphorylate purine substrates. When the structures of the human deoxyguanosine kinase (dGK, EC 2.7.1.113) and the dNK from Drosophila melanogaster were compared, a limited number of amino acid residues were identified and proposed to be responsible for the substrate specificity. Three of these key residues in Drosophila dNK were then mutagenized and the mutant enzymes were characterized regarding their ability to phosphorylate native deoxyribonucleosides and nucleoside analogs. The mutations converted the dNK substrate specificity from predominantly pyrimidine specific into purine specific. A similar scenario could have been followed during the evolution of kinases. Upon gene duplication of the progenitor kinase, only a limited number of single amino acid changes has taken place in each copy and resulted in substrate-specialized enzymes.
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http://dx.doi.org/10.1093/emboj/21.7.1873DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC125940PMC
April 2002
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