Structure of full-length class I chitinase from rice revealed by X-ray crystallography and small-angle X-ray scattering
Structure of full-length class I chitinase from rice revealed by X-ray crystallography and small-angle X-ray scattering
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DOI：
10.1002/prot.22742
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发表时间：
2010-08-01
影响因子：
2.9
通讯作者：
Nonaka, Takamasa
中科院分区：
文献类型：
--
作者：
Kezuka, Yuichiro;Kojima, Masaki;Nonaka, Takamasa
水稻I类几丁质酶OsChia 1b，也称为RCC 2或Cht-2，由N-末端几丁质结合结构域（ChBD）和C-末端催化结构域（CatD）组成，它们通过富含脯氨酸和苏氨酸的连接肽连接。由于OsChia 1b基因具有抑制真菌生长的能力，已被用于生产具有增强的抗病性的转基因植物。作为阐明水解作用和抗真菌活性机制的第一步，通过X射线晶体学和小角X射线散射（SAXS）分析了OsChia 1b的全长结构。我们在2.00埃的分辨率下确定了全长OsChia 1b的晶体结构，但是对于具有和不具有域间接触的生物分子有两种可能性。小角X射线衍射（SAXS）结果表明，OsChia 1b在溶液中的结构比晶体中的结构更复杂。这种延伸可能是由接头的构象柔性引起的。ChBD与三-N-乙酰壳三糖的对接模拟表现出类似的结合模式中观察到的一个两个结构域的植物凝集素与壳寡糖复合的晶体结构。基于结合模式的假设模型表明，ChBD不适合结合结晶α-几丁质，这是真菌细胞壁的主要成分，因为它与α-几丁质的平坦表面上的几丁质链的碰撞。该模型还表明GH 19几丁质酶的植物和细菌ChBD的结合特异性的差异，这有助于抗真菌活性。Proteins 2010; 78：2295-2305. (C)2010 Wiley-Liss，Inc.
The rice class I chitinase OsChia1b, also referred to as RCC2 or Cht-2, is composed of an N-terminal chitin-binding domain (ChBD) and a C-terminal catalytic domain (CatD), which are connected by a proline- and threonine-rich linker peptide. Because of the ability to inhibit fungal growth, the OsChia1b gene has been used to produce transgenic plants with enhanced disease resistance. As an initial step toward elucidating the mechanism of hydrolytic action and antifungal activity, the full-length structure of OsChia1b was analyzed by X-ray crystallography and small-angle X-ray scattering (SAXS). We determined the crystal structure of full-length OsChia1b at 2.00-angstrom resolution, but there are two possibilities for a biological molecule with and without interdomain contacts. The SAXS data showed an extended structure of OsChia1b in solution compared to that in the crystal form. This extension could be caused by the conformational flexibility of the linker. A docking simulation of ChBD with tri-N-acetylchitotriose exhibited a similar binding mode to the one observed in the crystal structure of a two-domain plant lectin complexed with a chitoo-ligosaccharide. A hypothetical model based on the binding mode suggested that ChBD is unsuitable for binding to crystalline alpha-chitin, which is a major component of fungal cell walls because of its collisions with the chitin chains on the flat surface of alpha-chitin. This model also indicates the difference in the binding specificity of plant and bacterial ChBDs of GH19 chitinases, which contribute to antifungal activity. Proteins 2010; 78:2295-2305. (C) 2010 Wiley-Liss, Inc.