Three-dimensional structure of Erwinia chrysanthemi pectin methylesterase reveals a novel esterase active site
Three-dimensional structure of Erwinia chrysanthemi pectin methylesterase reveals a novel esterase active site
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DOI：
10.1006/jmbi.2000.4324
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发表时间：
2001-01-26
影响因子：
5.6
通讯作者：
Pickersgill, RW
中科院分区：
文献类型：
--
作者：
Jenkins, J;Mayans, O;Pickersgill, RW
已发现大多数中性脂肪酶和酯酶结构采用常见的 α/β 水解酶折叠并包含催化性 Ser-His-Asp 三联体。整个蛋白质折叠和催化三联体的位置都发生一些变化，并且在一些酶中，天冬氨酸残基的作用被主链羰基氧原子取代。在这里，我们报道了果胶甲酯酶的晶体结构，该酶既不具有常见的α/β水解酶折叠，也不具有常见的催化三联体。菊欧文氏菌酶的结构通过多重同晶置换解析，并在 2.4 埃处精修至常规晶体学 X 因子 17.9%（不含 R 21.1%）。这是果胶甲酯酶的第一个结构，揭示了该酶包含右旋平行 β 螺旋，如在果胶裂解酶、果胶裂解酶、多聚半乳糖醛酸酶和鼠李糖半乳糖醛酸酶中所见，与鼠李糖半乳糖醛酸乙酰酯酶的 α/β 水解酶折叠不同，鼠李糖半乳糖醛酸乙酰酯酶与其共享酯酶活性。果胶甲酯酶与任何已知结构的蛋白质没有显着的序列相似性。果胶甲酯酶之间的序列保守性已映射到结构上，并揭示活性位点包含两个天冬氨酸残基和一个精氨酸残基。这些提出的催化残基位于平行β-螺旋的溶剂可及表面上以及由外部环形成的裂口中，其位置与果胶酸裂合酶的活性位点和底物结合裂口的位置相似。果胶甲酯酶的结构是新酯酶家族的一个例子。 (C) 2001 年学术出版社。
Most structures of neutral lipases and esterases have been found to adopt the common alpha/beta hydrolase fold and contain a catalytic Ser-His-Asp triad. Some variation occurs in both the overall protein fold and in the location of the catalytic triad, and in some enzymes the role of the aspartate residue is replaced by a main-chain carbonyl oxygen atom. Here, we report the crystal structure of pectin methylesterase that has neither the common alpha/beta hydrolase fold nor the common catalytic triad. The structure of the Erwinia chrysanthemi enzyme was solved by multiple isomorphous replacement and refined at 2.4 Angstrom to a conventional crystallographic X-factor of 17.9 % (R-free 21.1%). This is the first structure of a pectin methylesterase and reveals the enzyme to comprise a right-handed parallel beta -helix as seen in the pectinolytic enzymes pectate lyase, pectin lyase, polygalacturonase and rhamnogalacturonase, and unlike the alpha/beta hydrolase fold of rhamnogalacturonan acetylesterase with which it shares esterase activity. Pectin methylesterase has no significant sequence similarity with any protein of known structure. Sequence conservation among the pectin methylesterases has been mapped onto the structure and reveals that the active site comprises two aspartate residues and an arginine residue. These proposed catalytic residues, located on the solvent-accessible surface of the parallel beta -helix and in a cleft formed by external loops, are at a location similar to that of the active site and substrate-binding cleft of pectate lyase. The structure of pectin methylesterase is an example of a new family of esterases. (C) 2001 Academic Press.