myo-Inositol dehydrogenase and scyllo-inositol dehydrogenase from Lactobacillus casei BL23 bind their substrates in very different orientations
| Autor: | Drew Bertwistle, David A. R. Sanders, Hari Babu Aamudalapalli, David R. J. Palmer |
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| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
DNA Bacterial Lactobacillus casei Operon Stereochemistry Protein Conformation 030106 microbiology Biophysics Dehydrogenase Crystallography X-Ray Biochemistry Catalysis Analytical Chemistry 03 medical and health sciences Protein structure Bacterial Proteins Cloning Molecular Molecular Biology Ternary complex chemistry.chemical_classification biology food and beverages Active site Substrate (chemistry) Gene Expression Regulation Bacterial biology.organism_classification Recombinant Proteins Lacticaseibacillus casei Enzyme chemistry Genes Bacterial biology.protein Crystallization Inositol Sugar Alcohol Dehydrogenases |
| Zdroj: | Biochimica et biophysica acta. Proteins and proteomics. 1866(11) |
| ISSN: | 1878-1454 |
| Popis: | Many bacteria can use myo-inositol as the sole carbon source using enzymes encoded in the iol operon. The first step is catalyzed by the well-characterized myo-inositol dehydrogenase (mIDH), which oxidizes the axial hydroxyl group of the substrate to form scyllo-inosose. Some bacteria, including Lactobacillus casei, contain more than one apparent mIDH-encoding gene in the iol operon, but such redundant enzymes have not been investigated. scyllo-Inositol, a stereoisomer of myo-inositol, is not a substrate for mIDH, but scyllo-inositol dehydrogenase (sIDH) enzymes have been reported, though never observed to be encoded within the iol operon. Sequences indicate these enzymes are related, but the structural basis by which they distinguish their substrates has not been determined. Here we report the substrate selectivity, kinetics, and high-resolution crystal structures of the proteins encoded by iolG1 and iolG2 from L. casei BL23, which we show encode a mIDH and sIDH, respectively. Comparison of the ternary complex of each enzyme with its preferred substrate reveals the key variations allowing for oxidation of an equatorial versus an axial hydroxyl group. Despite the overall similarity of the active site residues, scyllo-inositol is bound in an inverted, tilted orientation by sIDH relative to the orientation of myo-inositol by mIDH. |
| Databáze: | OpenAIRE |
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