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Publication Abstract from PubMed

Chitinase C from Ralstonia sp. A-471 (Ra-ChiC) has a catalytic domain sequence similar to goose-type (G-type) lysozymes and, unlike other chitinases, belongs to glycohydrolase (GH) family 23. Using NMR spectroscopy, however, Ra-ChiC was found to interact only with the chitin dimer but not with the peptidoglycan fragment. Here we report the crystal structures of wild-type, E141Q, and E162Q of the catalytic domain of Ra-ChiC with or without chitin oligosaccharides. Ra-ChiC has a substrate-binding site including a tunnel-shaped cavity, which determines the substrate specificity. Mutation analyses based on this structural information indicated that a highly conserved Glu-141 acts as a catalytic acid, and that Asp-226 located at the roof of the tunnel activates a water molecule as a catalytic base. The unique arrangement of the catalytic residues makes a clear contrast to the other GH23 members and also to inverting GH19 chitinases.

Crystal Structures of the Catalytic Domain of a Novel Glycohydrolase Family 23 Chitinase from Ralstonia sp. A-471 Reveals a Unique Arrangement of the Catalytic Residues for Inverting Chitin Hydrolysis.,Arimori T, Kawamoto N, Shinya S, Okazaki N, Nakazawa M, Miyatake K, Fukamizo T, Ueda M, Tamada T J Biol Chem. 2013 Jun 28;288(26):18696-706. doi: 10.1074/jbc.M113.462135. Epub, 2013 May 8. PMID:23658014^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.