Identification of the substrate interaction region of the chitin-binding domain of Streptomyces griseus chitinase C
Identification of the substrate interaction region of the chitin-binding domain of Streptomyces griseus chitinase C
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DOI：
10.1093/jb/mvj062
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发表时间：
2006-03-01
影响因子：
2.7
通讯作者：
Ikegami, T
中科院分区：
文献类型：
--
作者：
Akagi, K;Watanabe, J;Ikegami, T
几丁质酶C是继高等植物中发现的几丁质酶之后，第一个从灰链霉菌hu6037中发现的细菌几丁质酶。几丁质酶C包括两个结构域：一个几丁质结合结构域（ChBD(ChiC)）用于附着几丁质，一个几丁质催化结构域用于消化几丁质。ChBD（ChiC）的结构通过C-13-、N-15-和h -1核磁共振（NMR）谱测定。其主链结构由2条和3条反平行β链组成的2个p -片组成，这与菊花Erwinia （CBDEGZ）的内切葡聚糖酶Z的纤维素结合结构域和Bacillus circulans WL-12的几丁质酶A1的几丁质结合结构域（ChBD(ChiA1)）的主链结构非常相似。通过化学位移扰动监测ChBD（ChiC）与六- n -乙酰壳己糖的相互作用，结果表明，ChBD（ChiC）与底物通过暴露在溶剂中的两个芳香环相互作用，而CBDEGZ与纤维素通过三个特征芳香环相互作用。ChBD（ChiA1）、ChBD（ChiC）和其他典型的几丁质和纤维素结合结构域的构象比较表明，它们具有三种溶剂暴露的芳香残基，负责与多糖结合，根据底物的不同，它们采用了多种结合位点构象，保留了几乎相同的主链构象。
Chitinase C from Streptomyces griseus HUT6037 was discovered as the first bacterial chitinase in family 19 other than chitinases found in higher plants. Chitinase C comprises two domains: a chitin-binding domain (ChBD(ChiC)) for attachment to chitin and a chitin-catalytic domain for digesting chitin. The structure of ChBD(ChiC) was determined by means of C-13-, N-15-, and H-1-resonance nuclear magnetic resonance (NMR) spectroscopy. The conformation of its backbone comprised two P-sheets composed of two and three antiparallel beta-strands, respectively, this being very similar to the backbone conformations of the cellulose-binding domain of endoglucanase Z from Erwinia chrysanthemi (CBDEGZ) and the chitin-binding domain of chitinase A1 from Bacillus circulans WL-12 (ChBD(ChiA1)). The interaction between ChBD(ChiC) and hexa-N-acetyl-chitohexaose was monitored through chemical shift perturbations, which showed that ChBDChiC interacted with the substrate through two aromatic rings exposed to the solvent as CBDEGZ interacts with cellulose through three characteristic aromatic rings. Comparison of the conformations of ChBD(ChiA1), ChBD(ChiC), and other typical chitin- and cellulose-binding domains, which have three solvent-exposed aromatic residues responsible for binding to polysaccharides, has suggested that they have adopted versatile binding site conformations depending on the substrates, with almost the same backbone conformations being retained.