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Tim Barrel

Burkhard Stoffels, Nils Sommer, Christine Berteld, Tim Vilz, Martin von Websky, Jörg C Kalff, Dimitrios Pantelis
INTRODUCTION: Complications following the creation of permanent intestinal ostomies are common and lead to serious problems in the stoma care of affected patients. The aim of this prospective, single-centre follow-up study was to record the rate of late complications in our own patient group and to identify potential risk factors. METHODS: All patients who received a permanent intestinal ostomy in our clinic within the period 2006 - 2016 were included in the study...
August 1, 2018: Zentralblatt Für Chirurgie
Gideon Lapidoth, Olga Khersonsky, Rosalie Lipsh, Orly Dym, Shira Albeck, Shelly Rogotner, Sarel J Fleishman
Automated design of enzymes with wild-type-like catalytic properties has been a long-standing but elusive goal. Here, we present a general, automated method for enzyme design through combinatorial backbone assembly. Starting from a set of homologous yet structurally diverse enzyme structures, the method assembles new backbone combinations and uses Rosetta to optimize the amino acid sequence, while conserving key catalytic residues. We apply this method to two unrelated enzyme families with TIM-barrel folds, glycoside hydrolase 10 (GH10) xylanases and phosphotriesterase-like lactonases (PLLs), designing 43 and 34 proteins, respectively...
July 17, 2018: Nature Communications
Lavanyaa Manjunath, Sai Rohit Guntupalli, Michael J Currie, Rachel A North, Renwick C J Dobson, Vinod Nayak, Ramaswamy Subramanian
Sialic acids are nine-carbon sugars that are found abundantly on the cell surfaces of mammals as glycoprotein or glycolipid complexes. Several Gram-negative and Gram-positive bacteria have the ability to scavenge and catabolize sialic acids to use as a carbon source. This gives them an advantage in colonizing sialic acid-rich environments. The genes of the sialic acid catabolic pathway are generally present as the operon nanAKE. The third gene in the operon encodes the enzyme N-acetylmannosamine-6-phosphate 2-epimerase (NanE), which catalyzes the conversion of N-acetylmannosamine 6-phosphate to N-acetylglucosamine 6-phosphate, thus committing it to enter glycolysis...
July 1, 2018: Acta Crystallographica. Section F, Structural Biology Communications
D Sean Froese, Jolanta Kopec, Elzbieta Rembeza, Gustavo Arruda Bezerra, Anselm Erich Oberholzer, Terttu Suormala, Seraina Lutz, Rod Chalk, Oktawia Borkowska, Matthias R Baumgartner, Wyatt W Yue
The folate and methionine cycles are crucial for biosynthesis of lipids, nucleotides and proteins, and production of the methyl donor S-adenosylmethionine (SAM). 5,10-methylenetetrahydrofolate reductase (MTHFR) represents a key regulatory connection between these cycles, generating 5-methyltetrahydrofolate for initiation of the methionine cycle, and undergoing allosteric inhibition by its end product SAM. Our 2.5 Å resolution crystal structure of human MTHFR reveals a unique architecture, appending the well-conserved catalytic TIM-barrel to a eukaryote-only SAM-binding domain...
June 11, 2018: Nature Communications
Jose Sergio Hleap, Christian Blouin
The Glycoside Hydrolase Family 13 (GH13) is both evolutionarily diverse and relevant to many industrial applications. Its members hydrolyze starch into smaller carbohydrates and members of the family have been bioengineered to improve catalytic function under industrial environments. We introduce a framework to analyze the response to selection of GH13 protein structures given some phylogenetic and simulated dynamic information. We find that the TIM-barrel (a conserved protein fold consisting of eight α-helices and eight parallel β-strands that alternate along the peptide backbone, common to all amylases) is not selectable since it is under purifying selection...
2018: PloS One
Lorena Tremiño, Alicia Forcada-Nadal, Vicente Rubio
Vitamin B6 -dependent genetic epilepsy was recently associated to mutations in PLPBP (previously PROSC), the human version of the widespread COG0325 gene that encodes TIM-barrel-like pyridoxal phosphate (PLP)-containing proteins of unclear function. We produced recombinantly, purified and characterized human PROSC (called now PLPHP) and its six missense mutants reported in epileptic patients. Normal PLPHP is largely a monomer with PLP bound through a Schiff-base linkage. The PLP-targeting antibiotic d-cycloserine decreased the PLP-bound peak as expected for pseudo-first-order reaction...
July 2018: Human Mutation
Mashkoor Alam, Abhishek Srivastava, Ankita Dutta, Apurba Kumar Sau
Despite importance of arginine decarboxylase (ADC: EC of Helicobacter pylori (H. pylori) 26695 pathogenic strain for acid adaptation in host, the enzyme has not yet been studied at a molecular level. Using combined approaches that include kinetic assays, site-directed mutagenesis, circular dichroism, heat-induced denaturation, analytical gel-filtration, and homology modeling, we report here a detailed investigation of H. pylori ADC. The pyridoxal 5'-phosphate (PLP)-dependent enzyme exhibits higher catalytic activity in the presence of Mg2+ ions at pH ∼8...
July 2018: IUBMB Life
Fei Zheng, Tao Tu, Xiaoyu Wang, Yuan Wang, Rui Ma, Xiaoyun Su, Xiangming Xie, Bin Yao, Huiying Luo
Background: Cellulases of glycosyl hydrolase (GH) family 5 share a (β/α)8 TIM-barrel fold structure with eight βα loops surrounding the catalytic pocket. These loops exposed on the surface play a vital role in protein functions, primarily due to the interactions of some key amino acids with solvent and ligand molecules. It has been reported that motions of these loops facilitate substrate access and product release, and loops 6 and 7 located at the substrate entrance of the binding pocket promote proton transfer reaction at the catalytic site motions...
2018: Biotechnology for Biofuels
Renata N Florindo, Valquiria P Souza, Lívia R Manzine, Cesar M Camilo, Sandro R Marana, Igor Polikarpov, Alessandro S Nascimento
Bifidobacterium is an important genus of probiotic bacteria colonizing the human gut. These bacteria can uptake oligosaccharides for the fermentative metabolism of hexoses and pentoses, producing lactate, acetate as well as short-chain fatty acids and propionate. These end-products are known to have important effects on human health. β-glucosidases (EC are pivotal enzymes for the metabolism and homeostasis of Bifidobacterium, since they hydrolyze small and soluble saccharides, typically producing glucose...
May 2018: Biochimie
Jennifer T Wang, Tim Stearns
The centriole is a defining feature of many eukaryotic cells. It nucleates a cilium, organizes microtubules as part of the centrosome, and is duplicated in coordination with the cell cycle. Centrioles have a remarkable structure, consisting of microtubules arranged in a barrel with ninefold radial symmetry. At their base, or proximal end, centrioles have unique triplet microtubules, formed from three microtubules linked to each other. This microtubule organization is not found anywhere else in the cell, is conserved in all major branches of the eukaryotic tree, and likely was present in the last eukaryotic common ancestor...
2017: Cold Spring Harbor Symposia on Quantitative Biology
Elshin J Mathias, Allanah Kenny, Michael J Plank, Tim David
A state-of-the-art integrated model of neurovascular coupling (NVC) (Dormanns et al., 2015b; Dormanns et al., 2016; Kenny et al., 2018) and the BOLD response (Mathias et al., 2017a; Mathias et al., 2017b) is presented with the ability to simulate the fMRI BOLD responses due to continuous neuronal spiking, bursting and cortical spreading depression (CSD) along with the underlying complex vascular coupling. Simulated BOLD responses are compared to experimental BOLD signals observed in the rat barrel cortex and in the hippocampus under seizure conditions showing good agreement...
July 1, 2018: NeuroImage
Wei Zhang, Yueyang Xu, Mengrong Yan, Shanshan Li, Huiying Wang, Haitao Yang, Weihong Zhou, Zihe Rao
Endonuclease IV is a typical endonuclease of the apurinic-apyrimidinic (AP) or abasic endonuclease superfamily. It repairs damaged DNA through base excision repair by cleaving the DNA backbone immediately 5' of an AP site. In Mycobacterium tuberculosis, endonuclease IV is the major AP endonuclease. This enzyme is absent from mammalian cells, making it an attractive target for anti-tuberculosis drug development. In this study, the structure of the recombinant endonuclease IV from M. tuberculosis (MtbEndo IV) was determined at a high resolution of 1...
March 25, 2018: Biochemical and Biophysical Research Communications
Tripti Dadheech, Ravi Shah, Ramesh Pandit, Ankit Hinsu, Prakram Singh Chauhan, Subhash Jakhesara, Anju Kunjadiya, Dharamshibhai Rank, Chaitanya Joshi
Cellulase hydrolyses the cellulose by cleaving the β-1,4-linkages to produce mono-, oligo- and shorter polysaccharide units. These enzymes have applications in various industries such as pulp and paper, laundry, food and feed, textile, brewing industry and in biofuel production. In the present study we have cloned acid-cellulase gene (Cel-1) from the fosmid library of buffalo rumen metagenomic DNA and functionally expressed it in Escherichia coli. The ORF encoding cellulase consisted of 1176-bp, corresponding to protein of 391 amino acid and has catalytic domain belonging to glycosyl hydrolase family 5...
July 1, 2018: International Journal of Biological Macromolecules
Kirk E Hevener, Bernard D Santarsiero, Hyun Lee, Jesse A Jones, Teuta Boci, Michael E Johnson, Shahila Mehboob
Enoyl-acyl carrier protein (ACP) reductase II (FabK) is a critical rate-limiting enzyme in the bacterial type II fatty-acid synthesis (FAS II) pathway. FAS II pathway enzymes are markedly disparate from their mammalian analogs in the FAS I pathway in both structure and mechanism. Enzymes involved in bacterial fatty-acid synthesis represent viable drug targets for Gram-negative pathogens, and historical precedent exists for targeting them in the treatment of diseases of the oral cavity. The Gram-negative organism Porphyromonas gingivalis represents a key causative agent of the costly and highly prevalent disease known as chronic periodontitis, and exclusively expresses FabK as its enoyl reductase enzyme in the FAS-II pathway...
February 1, 2018: Acta Crystallographica. Section F, Structural Biology Communications
Kazuhiro Yamada, Markos Koutmos
Methyl transfer between methyltetrahydrofolate and corrinoid molecules is a key reaction in biology that is catalyzed by a number of enzymes in many prokaryotic and eukaryotic organisms. One classic example of such an enzyme is cobalamin-dependent methionine synthase (MS). MS is a large modular protein that utilizes an SN 2-type mechanism to catalyze the chemically challenging methyl transfer from the tertiary amine (N5) of methyltetrahydrofolate to homocysteine in order to form methionine. Despite over half a century of study, many questions remain about how folate-dependent methyltransferases, and MS in particular, function...
January 1, 2018: Acta Crystallographica. Section D, Structural Biology
Bo Lv, Hanli Sun, Shen Huang, Xudong Feng, Tao Jiang, Chun Li
Glycoside hydrolases (GHs) have attracted special attention in research aimed at modifying natural products by partial removal of sugar moieties to manipulate their solubility and efficacy. However, these modifications are challenging to control because the low substrate specificity of most GHs often generates undesired by-products. We previously identified a GH2-type fungal β-glucuronidase from Aspergillus oryzae ( P GUS) exhibiting promiscuous substrate specificity in hydrolysis of triterpenoid saponins...
January 12, 2018: Journal of Biological Chemistry
Philemon Stavros, Piotr H Malecki, Maria Theodoridou, Wojciech Rypniewski, Constantinos E Vorgias, George Nounesis
Chitinase 60 from the psychrophilic bacterium Moritella marina (MmChi60) is a four-domain protein whose structure revealed flexible hinge regions between the domains, yielding conformations in solution that range from fully extended to compact. The catalytic domain is a shallow-grooved TIM-barrel. Heat-induced denaturation experiments of the wild-type and mutants resulting from the deletions of the two-Ig-like domains and the chitin binding domain reveal calorimetric profiles that are consistent with non-collaborative thermal unfolding of the individual domains, a property that must be associated to the "hinge-regions"...
September 2015: Biochemistry and Biophysics Reports
Victoria J Laye, Ram Karan, Jong-Myoung Kim, Wolf T Pecher, Priya DasSarma, Shiladitya DasSarma
The Antarctic microorganism Halorubrum lacusprofundi harbors a model polyextremophilic β-galactosidase that functions in cold, hypersaline conditions. Six amino acid residues potentially important for cold activity were identified by comparative genomics and substituted with evolutionarily conserved residues (N251D, A263S, I299L, F387L, I476V, and V482L) in closely related homologs from mesophilic haloarchaea. Using a homology model, four residues (N251, A263, I299, and F387) were located in the TIM barrel around the active site in domain A, and two residues (I476 and V482) were within coiled or β-sheet regions in domain B distant to the active site...
November 21, 2017: Proceedings of the National Academy of Sciences of the United States of America
William J Bradshaw, Jonathan M Kirby, April K Roberts, Clifford C Shone, K Ravi Acharya
Clostridium difficile is a burden to healthcare systems around the world, causing tens of thousands of deaths annually. The S-layer of the bacterium, a layer of protein found of the surface of cells, has received a significant amount of attention over the past two decades as a potential target to combat the growing threat presented by C. difficile infections. The S-layer contains a wide range of proteins, each of which possesses three cell wall-binding domains, while many also possess a "functional" region...
December 2017: FEBS Journal
Rajashekar Varma Kadumuri, Ramakrishna Vadrevu
The (βα)8/TIM barrel is one of the most common folds of known protein structures facilitating diverse catalytic functions. The fold is formed by the repetition of the basic βαβ building block in which the β-strands are followed by α-helices eight times alternating in sequence and structure. αβ and βα loops connecting α-helices to the β-strands and the β-strands to the α-helices contribute to stability and function, respectively, an inherent imposition by the TIM barrel architecture itself. In this study, αβ and βα loops from a data set of 430 non-redundant, high-resolution triosephosphate isomerase (TIM) barrels bearing sequence homology of <30% were analyzed for their amino acid propensities, sequence profiles, and positional preferences of amino acids...
October 24, 2017: Interdisciplinary Sciences, Computational Life Sciences
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