STRUCTURE OF UNCOMPLEXED AND LINOLEATE-BOUND CANDIDA-CYLINDRACEA CHOLESTEROL ESTERASE
STRUCTURE OF UNCOMPLEXED AND LINOLEATE-BOUND CANDIDA-CYLINDRACEA CHOLESTEROL ESTERASE
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DOI：
10.1016/s0969-2126(01)00158-7
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发表时间：
1995-03-15
期刊：
影响因子：
5.7
通讯作者：
DUAX, WL
中科院分区：
文献类型：
--
作者：
GHOSH, D;WAWRZAK, Z;DUAX, WL
背景：圆筒假丝酵母菌的胆固醇酯酶(CE)与三酰甘油酰基水解酶和胆碱酯酶具有相同的α/β水解酶超家族。已被X射线结晶学研究的其他家族成员包括加州鱼雷乙酰胆碱酯酶、白地霉脂肪酶和念珠菌皱纹假丝酵母脂肪酶。CE与三酰甘油酰基水解酶同源，序列同源性为89%。结果：分别在1.9埃和2.0埃分辨率下测定了未络合和亚油酸结合的CE的结构，揭示了单体的二聚体缔合，其中两个活性中心峡谷面对面，将疏水表面屏蔽在水环境中。脂肪链被埋在活性中心附近的一个很深的疏水口袋里。底物的胆固醇基团的位置不明确，但可以在二聚体界面的疏水核心处模拟。结论：复杂晶型和非络合晶型的单体结构是相同的。二聚体在二聚体界面上的两个单体的相对位置不同。在CE中的55个残基中，有23个位于活性部位和二聚体界面。底物专一性的改变是这些替换的直接结果。
Background: Candida cylindracea cholesterol esterase (CE) reversibly to the same alpha/beta hydrolase superfamily as triacylglycerol acyl hydrolases and cholinesterases. Other members of the family that have been studied by X-ray crystallography include Torpedo californica acetylcholinesterase, Geotrichum candidum lipase and Candida rugose lipase. CE is homologous to C. rugosa lipase 1, triacylglycerol acyl hydrolase, with which it shares 89% sequence identity. The present study explores the details of dimer formation of CE and the basis for its substrate specificity.Results: The structures of uncomplexed and linoleate-bound CE determined at 1.9 Angstrom and 2.0 Angstrom resolution , respectively, reveal a dimeric association of monomers in which two active-site gorges face each other, shielding hydrophobic surfaces from the aqueous environment. The fatty-acid chain is buried in a deep hydrophobic pocket near the active site. The positioning of the cholesteryl moiety of the substrate is equivocal, but could be modeled in the hydrophobic core of the dimer interface.Conclusions: The monomer structure is the same in both the complex and uncomplexed crystal forms. The dimers differ in the relative positions of the two monomers at the dimer interface. Of the 55 residues that are different in CE from those in C. rugosa lipase 1, 23 are located in the active site and at the dimer interface. The altered substrate specificity is a direct consequence of these substitutions.