Dataset Information

Insights into role of the hydrogen bond networks in substrate recognition by UDP-GalNAc 4-epimerases.

ABSTRACT: UDP-hexose 4-epimerases are critical in galactose metabolism and often important in lipopolysaccharide biosynthesis as well. Three groups of these enzymes have been reported based on their substrate specificity towards non-acetylated substrates (group 1), dual specificity towards N-acetylated and non-acetylated substrates (group 2) and specificity towards N-acetylated substrates (group 3). We recently reported the structure of a novel UDP-GalNAc 4-epimerase called WbgU and based on the structure proposed a model of specific substrate recognition by UDP-GalNAc 4-epimerases. In this work, we present an analysis of the proposed model of substrate recognition using site-directed mutagenesis of WbgU and crystal structure of the His305Ala mutant. This investigation reveals that the wild-type activity of WbgU is retained in most single-point mutants targeting the active site. However, a graded loss in activity is observed in double-and triple-point mutants with the quadruple-point mutant being completely inactive corroborating the proposed rationale of substrate recognition. Furthermore, crystal structure of the His305Ala mutant shows that the structure is significantly similar to the wild-type WbgU, albeit a loss in the critical hydrogen bond network seated at His305 and ensuing minor conformational changes. It is inferred that the specific and non-specific interactions throughout the active site confer it sufficient elasticity to sustain wild-type activity for several of the single-point mutations.

SUBMITTER: Bhatt VS

PROVIDER: S-EPMC3441825 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature

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Insights into role of the hydrogen bond networks in substrate recognition by UDP-GalNAc 4-epimerases.

Bhatt Veer Sandeep VS Guan Wanyi W Xue Mengyang M Yuan Huiqing H Wang Peng George PG

Biochemical and biophysical research communications 20110723 2

UDP-hexose 4-epimerases are critical in galactose metabolism and often important in lipopolysaccharide biosynthesis as well. Three groups of these enzymes have been reported based on their substrate specificity towards non-acetylated substrates (group 1), dual specificity towards N-acetylated and non-acetylated substrates (group 2) and specificity towards N-acetylated substrates (group 3). We recently reported the structure of a novel UDP-GalNAc 4-epimerase called WbgU and based on the structure ...[more]

PMID: 21810411

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Project description:Hydrogen-bonding networks in proteins considered as structural tensile elements are in balance separately from any other stabilising interactions that may be in operation. The hydrogen bond arrangement in the network is reminiscent of tensegrity structures in architecture and sculpture. Tensegrity has been discussed before in cells and tissues and in proteins. In contrast to previous work only hydrogen bonds are studied here. The other interactions within proteins are either much stronger - covalent bonds connecting the atoms in the molecular skeleton or weaker forces like the so-called hydrophobic interactions. It has been demonstrated that the latter operate independently from hydrogen bonds. Each category of interaction must, if the protein is to have a stable structure, balance out. The hypothesis here is that the entire hydrogen bond network is in balance without any compensating contributions from other types of interaction. For sidechain-sidechain, sidechain-backbone and backbone-backbone hydrogen bonds in proteins, tensegrity balance ("closure") is required over the entire length of the polypeptide chain that defines individually folding units in globular proteins ("domains") as well as within the repeating elements in fibrous proteins that consist of extended chain structures. There is no closure to be found in extended structures that do not have repeating elements. This suggests an explanation as to why globular domains, as well as the repeat units in fibrous proteins, have to have a defined number of residues. Apart from networks of sidechain-sidechain hydrogen bonds there are certain key points at which this closure is achieved in the sidechain-backbone hydrogen bonds and these are associated with demarcation points at the start or end of stretches of secondary structure. Together, these three categories of hydrogen bond achieve the closure that is necessary for the stability of globular protein domains as well as repeating elements in fibrous proteins.

Dataset Information

Insights into role of the hydrogen bond networks in substrate recognition by UDP-GalNAc 4-epimerases.

Publications

Insights into role of the hydrogen bond networks in substrate recognition by UDP-GalNAc 4-epimerases.

Similar Datasets

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