Kusuma School of Biological Sciences, Indian Institute of Technology Delhi, New Delhi, 110016, India.
Raja Ramanna Centre for Advanced Technology, Indore, 452 013, India.
Phytochemistry. 2020 Feb;170:112221. doi: 10.1016/j.phytochem.2019.112221. Epub 2019 Nov 29.
The ICChI is a 35-kDa, glycosylated protein isolated from the latex of the weed Ipomoea carnea. It displays chitinase and lysozyme activity, which could be important for the defense against pathogenic fungi, insects and bacteria. The ICChI enzyme was crystallized, and a diffraction data set was collected from a single crystal to 1.42 Å resolution. The crystals belong to the primitive tetragonal space group P422, with unit-cell parameters a = b = 57.9, c = 172.0 Å, and α = β = γ = 90°. The structure was elucidated by molecular replacement method using a mixed model of three homologous structures from the N-terminal sequence of ICChI. The refined model consists of 272 amino acid residues and has a R of 18.93% and R of 22.42%. The protein consists of a single globular domain with a (α/β) triosephosphate isomerase barrel fold. Three of the consensus sites for N-glycosylation viz., Asn, Asn, and Asn containing carbohydrate moieties N-Acetylglucosamine (NAG), mannose, fucose, and xylose. The putative catalytic residues are Asp, Glu, and Tyr. The crystal structure may provide fundamental information of GH18 family chitinases.
ICChI 是一种 35kDa 的糖基化蛋白，从杂草Ipomoea carnea 的乳汁中分离得到。它显示出几丁质酶和溶菌酶的活性，这对于防御病原真菌、昆虫和细菌可能很重要。ICChI 酶已结晶，并从单个晶体中收集到 1.42Å 的衍射数据集。晶体属于原始四方空间群 P422，具有单元胞参数 a=b=57.9，c=172.0Å，α=β=γ=90°。该结构通过分子置换法用 ICChI 的 N 端序列的三个同源结构的混合模型阐明。经修正的模型由 272 个氨基酸残基组成，R 值为 18.93%，R 值为 22.42%。该蛋白由单个球状结构域组成，具有（α/β）磷酸丙糖异构酶桶折叠。三个公认的 N-糖基化位点分别为含有碳水化合物部分 N-乙酰葡萄糖胺（NAG）、甘露糖、岩藻糖和木糖的 Asn、Asn 和 Asn。假定的催化残基为 Asp、Glu 和 Tyr。晶体结构可能为 GH18 家族几丁质酶提供基本信息。
