Simms S A, Keane M G, Stock J
J Biol Chem. 1985 Aug 25;260(18):10161-8.
The methylesterase which catalyzes demethylation of chemotactic membrane receptors in Salmonella typhimurium has been purified and characterized. Two forms of the enzyme have been isolated from cell extracts. One corresponds in molecular weight, Mr = 37,000, and amino acid composition to the predicted product of the structural gene for the methylesterase, cheB. The other is a proteolytic fragment, Mr = 21,000, corresponding to the C-terminal three-fifths of the intact CheB protein. The specific activity of the 21-kDa enzyme is at least 15-fold greater than that of its 37-kDa precursor. We conclude that the CheB protein is composed of at least two structurally distinct portions: a C-terminal catalytic domain, and an N-terminal region which modulates esterase activity.
催化鼠伤寒沙门氏菌趋化性膜受体去甲基化的甲基酯酶已被纯化并进行了特性分析。已从细胞提取物中分离出该酶的两种形式。一种在分子量（Mr = 37,000）和氨基酸组成上与甲基酯酶结构基因cheB的预测产物相对应。另一种是蛋白水解片段，Mr = 21,000，对应于完整CheB蛋白的C端五分之三。21 kDa酶的比活性至少比其37 kDa前体高15倍。我们得出结论，CheB蛋白至少由两个结构不同的部分组成：一个C端催化结构域和一个调节酯酶活性的N端区域。
