3lmw

Crystal structure of iota-carrageenase family GH82 from A. fortis in absence of chloride ions

spinqualitylabelsall models 3lmw, resolution 2.60Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3lmw is a 2 chain structure with sequence from Altfo. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: CA, NI, NO3 Related: 1h80, 1ktw Gene: cgiA (ALTFO) Activity: Iota-carrageenase, with EC number 3.2.1.157 Resources: FirstGlance, OCA, RCSB, PDBsum Function [CGIA_ALTFO] Hydrolyzes iota-carrageenans, sulfated 1,3-alpha-1,4-beta galactans from red algal cell walls, with an inversion of anomeric configuration. Also active against hybrid iota-/nu-carrageenan, not active against kappa- or lambda-carrageenans. [UniProtKB:Q9F284] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed Marine polysaccharide degrading enzymes, and iota-carrageenases in particular, have received little attention in the past, although their substrate specificity is of interest for biotechnological applications. This is mostly a consequence of the lack of data about their occurrence in the marine environment. Recent metagenomic data mining and the genome sequencing of a marine bacterium, Zobellia galactanivorans, led to the identification of three new iota-carrageenase genes belonging to the glycoside hydrolase family GH82. The additional sequences helped identify potential candidate residues as catalytic proton donor and nucleophile. We have identified the catalytic key residues experimentally by site directed mutagenesis and subsequent kinetic analysis for the iota-carrageenase from Alteromonas fortis CgiA1_Af. The kinetic analyses of the purified mutant enzymes confirm that E245 plays the role of the catalytic proton donor and D247 the general base that activates the catalytic water molecule. The point mutations of three other residues, namely Q222, H281 and Q310 in A. fortis, located in proximity of the active site also affect the enzyme activity. Our results indicate that E310 plays a role in stabilizing the substrate intermediate conformation, while H281 is involved in substrate binding and appears crucial for maintaining the protonation state of the catalytic proton donor E245. The third residue, Q222 that bridges the catalytic water molecule and a chloride ion, plays a crucial role in structuring the water network in the active site of A. fortis iota-carrageenase. Identification of catalytic residues and mechanistic analysis of family GH82 iota-carrageenases.,Rebuffet E, Barbeyron T, Jeudy A, Jam M, Czjzek M, Michel G Biochemistry. 2010 Aug 3. PMID:20681629 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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