Structural highlights
Publication Abstract from PubMedDESCRIPTIONS: The structure of a GH19 chitinase from the moss Bryum coronatum (BcChi-A) in complex with the substrate was examined by X-ray crystallography and NMR spectroscopy in solution. The X-ray crystal structure of the inactive mutant of BcChi-A (BcChi-A-E61A) liganded with chitin tetramer (GlcNAc)4 revealed a clear electron density of the tetramer bound to subsites -2, -1, +1, and +2. Individual sugar residues were recognized by several amino acids at these subsites through a number of hydrogen bonds. This is the first crystal structure of GH19 chitinase liganded with oligosaccharide spanning the catalytic center. NMR titration experiments of chitin oligosaccharides into the BcChi-A-E61A solution showed that the binding mode observed in the crystal structure is similar to that in solution. The C-1 carbon of -1 GlcNAc, the Oepsilon1 atom of the catalytic base (Glu70), and the Ogamma atom of Ser102 form a "triangle" surrounding the catalytic water, and the arrangement structurally validated the proposed catalytic mechanism of GH19 chitinases. The glycosidic linkage between -1 and +1 sugars was found to be twisted and under strain. This situation may contribute to the reduction of activation energy for hydrolysis. The complex structure revealed a more refined mechanism of the chitinase catalysis. Crystal structure of a "loopless" GH19 chitinase in complex with chitin tetrasaccharide spanning the catalytic center.,Ohnuma T, Umemoto N, Nagata T, Shinya S, Numata T, Taira T, Fukamizo T Biochim Biophys Acta. 2014 Feb 25;1844(4):793-802. doi:, 10.1016/j.bbapap.2014.02.013. PMID:24582745[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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