Functional Analysis of the Chitin-binding Domain of a Family 19 Chitinase from Streptomyces griseus HUT6037 : Substrate-binding Affinity and cis-Dominant Increase of Antifungal Function(Biochemistry & Molecular Biology)

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Chitinase C (ChiC) is the first bacterial family 19 chitinase discovered in Streptomyces griseus HUT6037. While it shares significant similarity with the plant family 19 chitinases in the catalytic domain, its N-terminal chitin-binding domain (ChBD_<ChiC>) differs from those of the plant enzymes. ChBD_<ChiC> and the catalytic domain (CatD_<ChiC>), as well as intact ChiC, were separately produced in E. coli and purified to homogeneity. Binding experiments and isothermal titration calorimetry assays demonstrated that ChBD_<ChiC> binds to insoluble chitin, soluble chitin, cellulose, and N-acetylchitohexaose (roughly in that order). A deletion of ChBD_<ChiC> resulted in moderate (about 50%) reduction of the hydrolyzing activity toward insoluble chitin substrates, but most (about 90%) of the antifungal activity against Trichoderma reesei was abolished by this deletion. Thus, this domain appears to contribute more importantly to antifungal properties than to catalytic activities. ChBD_<ChiC> itself did not have antifungal activity or a synergistic effect on the antifungal activity of CatD_<ChiC> in trans.
社団法人日本農芸化学会の論文
2002-05-23