scholarly journals Mapping of barley α-amylases and outer subsite mutants reveals dynamic high-affinity subsites and barriers in the long substrate binding cleft

FEBS Letters ◽  
2006 ◽  
Vol 580 (21) ◽  
pp. 5049-5053 ◽  
Author(s):  
Lili Kandra ◽  
Maher Abou Hachem ◽  
Gyöngyi Gyémánt ◽  
Birte Kramhøft ◽  
Birte Svensson
Keyword(s):  
Substrate Binding ◽  
High Affinity ◽  
Binding Cleft

scholarly journals Deamidation and glycation of a Bacillus licheniformis α-amylase during industrial fermentation can improve detergent wash performance

Amylase ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 38-49
Author(s):  
Connie Pontoppidan ◽  
Svend G. Kaasgaard ◽  
Carsten P. Sønksen ◽  
Carsten Andersen ◽  
Birte Svensson
Keyword(s):  
Bacillus Licheniformis ◽  
Mutational Analysis ◽  
Peptide Mapping ◽  
Substrate Binding ◽  
Carbohydrate Binding ◽  
Surface Binding ◽  
Lysine Residues ◽  
Tandem Mass Spectrometric ◽  
Binding Cleft ◽  
Household Detergents

Abstract The industrial thermostable Bacillus licheniformis α-amylase (BLA) has wide applications, including in household detergents, and efforts to improve its performance are continuously ongoing. BLA during the industrial production is deamidated and glycated resulting in multiple forms with different isoelectric points. Forty modified positions were identified by tandem mass spectrometric peptide mapping of BLA forms separated by isoelectric focusing. These modified 12 asparagine, 9 glutamine, 8 arginine and 11 lysine residues are mostly situated on the enzyme surface and several belong to regions involved in stability, activity and carbohydrate binding. Eight residues presumed to interact with starch at the active site and surface binding sites (SBSs) were subjected to mutational analysis. Five mutants mimicking deamidation (N→D, Q→E) at the substrate binding cleft showed moderate to no effect on thermostability and k cat and K M for maltoheptaose and amylose. Notably, the mutations improved laundry wash efficiency in detergents at pH 8.5 and 10.0. Replacing three reducing sugar reactive side chains (K→M, R→L) at a distant substrate binding region and two SBSs enhanced wash performance especially in liquid detergent at pH 8.5, slightly improved enzymatic activity and maintained thermostability. Wash performance was most improved (5-fold) for the N265D mutant near substrate binding subsite +3.

Chitosanase from Streptomyces sp. strain N174: a comparative review of its structure and function

1997 ◽  
Vol 75 (6) ◽  
pp. 687-696 ◽  
Author(s):  
Tamo Fukamizo ◽  
Ryszard Brzezinski
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Substrate Binding ◽  
Structure And Function ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Streptomyces Sp ◽  
Binding Cleft ◽  
And Function

Novel information on the structure and function of chitosanase, which hydrolyzes the beta -1,4-glycosidic linkage of chitosan, has accumulated in recent years. The cloning of the chitosanase gene from Streptomyces sp. strain N174 and the establishment of an efficient expression system using Streptomyces lividans TK24 have contributed to these advances. Amino acid sequence comparisons of the chitosanases that have been sequenced to date revealed a significant homology in the N-terminal module. From energy minimization based on the X-ray crystal structure of Streptomyces sp. strain N174 chitosanase, the substrate binding cleft of this enzyme was estimated to be composed of six monosaccharide binding subsites. The hydrolytic reaction takes place at the center of the binding cleft with an inverting mechanism. Site-directed mutagenesis of the carboxylic amino acid residues that are conserved revealed that Glu-22 and Asp-40 are the catalytic residues. The tryptophan residues in the chitosanase do not participate directly in the substrate binding but stabilize the protein structure by interacting with hydrophobic and carboxylic side chains of the other amino acid residues. Structural and functional similarities were found between chitosanase, barley chitinase, bacteriophage T4 lysozyme, and goose egg white lysozyme, even though these proteins share no sequence similarities. This information can be helpful for the design of new chitinolytic enzymes that can be applied to carbohydrate engineering, biological control of phytopathogens, and other fields including chitinous polysaccharide degradation. Key words: chitosanase, amino acid sequence, overexpression system, reaction mechanism, site-directed mutagenesis.

scholarly journals The activation loop and substrate-binding cleft of glutaminase C are allosterically coupled

2019 ◽  
Vol 295 (5) ◽  
pp. 1328-1337
Author(s):  
Yunxing Li ◽  
Sekar Ramachandran ◽  
Thuy-Tien T. Nguyen ◽  
Clint A. Stalnecker ◽  
Richard A. Cerione ◽  
...  
Keyword(s):  
Substrate Binding ◽  
Fluorescence Emission ◽  
Reciprocal Relationship ◽  
Tryptophan Residue ◽  
Substrate Affinity ◽  
Activation Loop ◽  
Conformational Coupling ◽  
Binding Cleft ◽  
Glutaminase Activity

The glutaminase C (GAC) isoform of mitochondrial glutaminase is overexpressed in many cancer cells and therefore represents a potential therapeutic target. Understanding the regulation of GAC activity has been guided by the development of spectroscopic approaches that measure glutaminase activity in real time. Previously, we engineered a GAC protein (GAC(F327W)) in which a tryptophan residue is substituted for phenylalanine in an activation loop to explore the role of this loop in enzyme activity. We showed that the fluorescence emission of Trp-327 is enhanced in response to activator binding, but quenched by inhibitors of the BPTES class that bind to the GAC tetramer and contact the activation loop, thereby constraining it in an inactive conformation. In the present work, we took advantage of a tryptophan substitution at position 471, proximal to the GAC catalytic site, to examine the conformational coupling between the activation loop and the substrate-binding cleft, separated by ∼16 Å. Comparison of glutamine binding in the presence or absence of the BPTES analog CB-839 revealed a reciprocal relationship between the constraints imposed on the activation loop position and the affinity of GAC for substrate. Binding of the inhibitor weakened the affinity of GAC for glutamine, whereas activating anions such as Pi increased this affinity. These results indicate that the conformations of the activation loop and the substrate-binding cleft in GAC are allosterically coupled and that this coupling determines substrate affinity and enzymatic activity and explains the activities of CB-839, which is currently in clinical trials.

scholarly journals Spatially remote motifs cooperatively affect substrate preference of a ruminal GH26-type endo-β-1,4-mannanase

2020 ◽  
Vol 295 (15) ◽  
pp. 5012-5021 ◽  
Author(s):  
Fernanda Mandelli ◽  
Mariana Abrahão Bueno de Morais ◽  
Evandro Antonio de Lima ◽  
Leane Oliveira ◽  
Gabriela Felix Persinoti ◽  
...  
Keyword(s):  
Catalytic Domain ◽  
Substrate Binding ◽  
Substrate Recognition ◽  
Systematic Investigation ◽  
Substrate Preference ◽  
Carbohydrate Binding ◽  
Carbohydrate Binding Modules ◽  
Binding Cleft ◽  
Aromatic Cluster ◽  
Shed Light

β-Mannanases from the glycoside hydrolase 26 (GH26) family are retaining hydrolases that are active on complex heteromannans and whose genes are abundant in rumen metagenomes and metatranscriptomes. These enzymes can exhibit distinct modes of substrate recognition and are often fused to carbohydrate-binding modules (CBMs), resulting in a molecular puzzle of mechanisms governing substrate preference and mode of action that has not yet been pieced together. In this study, we recovered a novel GH26 enzyme with a CBM35 module linked to its N terminus (CrMan26) from a cattle rumen metatranscriptome. CrMan26 exhibited a preference for galactomannan as substrate and the crystal structure of the full-length protein at 1.85 Å resolution revealed a unique orientation of the ancillary domain relative to the catalytic interface, strategically positioning a surface aromatic cluster of the ancillary domain as an extension of the substrate-binding cleft, contributing to galactomannan preference. Moreover, systematic investigation of nonconserved residues in the catalytic interface unveiled that residues Tyr195 (−3 subsite) and Trp234 (−5 subsite) from distal negative subsites have a key role in galactomannan preference. These results indicate a novel and complex mechanism for substrate recognition involving spatially remote motifs, distal negative subsites from the catalytic domain, and a surface-associated aromatic cluster from the ancillary domain. These findings expand our molecular understanding of the mechanisms of substrate binding and recognition in the GH26 family and shed light on how some CBMs and their respective orientation can contribute to substrate preference.

scholarly journals Two perfectly conserved arginine residues are required for substrate binding in a high-affinity nitrate transporter

2004 ◽  
Vol 101 (50) ◽  
pp. 17549-17554 ◽  
Author(s):  
S. E. Unkles ◽  
D. A. Rouch ◽  
Y. Wang ◽  
M. Y. Siddiqi ◽  
A. D. M. Glass ◽  
...  
Keyword(s):  
Substrate Binding ◽  
Nitrate Transporter ◽  
High Affinity ◽  
Arginine Residues

Cofactor and Substrate Binding to Vanadium Chloroperoxidase Determined by UV−VIS Spectroscopy and Evidence for High Affinity for Pervanadate†

Biochemistry ◽  
2000 ◽  
Vol 39 (5) ◽  
pp. 1133-1141 ◽  
Author(s):  
Rokus Renirie ◽  
Wieger Hemrika ◽  
Sander R. Piersma ◽  
Ron Wever
Keyword(s):  
Substrate Binding ◽  
High Affinity ◽  
Vis Spectroscopy

scholarly journals To be, or not to be two sites: that is the question about LeuT substrate binding

2011 ◽  
Vol 138 (4) ◽  
pp. 467-471 ◽  
Author(s):  
Nicolas Reyes ◽  
Sotiria Tavoulari
Keyword(s):  
Binding Sites ◽  
Journal Club ◽  
Substrate Binding ◽  
Structural Data ◽  
Transport Proteins ◽  
Model System ◽  
Transport Mechanisms ◽  
High Affinity ◽  
The Central Nervous System ◽  
Substrate Binding Sites

Transport proteins of the neurotransmitter sodium symporter (NSS) family regulate the extracellular concentration of several neurotransmitters in the central nervous system. The only member of this family for which atomic-resolution structural data are available is the prokaryotic homologue LeuT. This protein has been used as a model system to study the molecular mechanism of transport of the NSS family. In this Journal Club, we discuss two strikingly different LeuT transport mechanisms: one involving a single high-affinity substrate binding site and one recently proposed alternative involving two high-affinity substrate binding sites that are allosterically coupled.

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