Elucidation of structure and function relationship in multiple-domain chitinases probed by a combination of X-ray crystallography, solution scattering, and molecular dynamics simulation

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We suggest a hypothetical binding model of chitin-binding domains of Cht2 and ChiC, members of glycoside hydrolase family 19, against crystallineα-chitin. This model indicates the difference in the binding specificity of two chitinases. In both chitinases, the conformational flexibility of the interdomain linker can be considered to cause the conformational extension and the variability of the domain arrangement. These results tempt us to speculate the following mechanism of chitin degradation. While ChBD binds to chitin chain and acts as an anchor, CatD degrades chitin chains within a defined region of the radius depending on linker length.We determined and refined the crystal structures of the catalytic domain of chitinase D and its inhibitor complex. It is shown that conformational change of a substrate-binding loop is induced by the inhibitor binding.