The structure of E. coli beta-galactosidase.
The structure of E. coli beta-galactosidase.
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作者：
B. Matthews
大肠杆菌β-半乳糖苷酶是由四个相同的1023个氨基酸组成的四聚体。每条链由五个结构域组成，其中第三个结构域是一个八链的α/β桶，它包含了大部分活性部位。然而，这个站点确实包含来自其他域和其他子单元的元素。多肽链的N-末端区域有助于形成一个亚单位界面。综上所述，这些特征为众所周知的阿尔法互补特性提供了结构基础。催化活性是通过与Glu537形成共价半乳糖中间体来进行的，包括底物结合的“浅”和“深”模式。
E. coli beta-galactosidase is a tetramer of four identical 1023-amino acid chains. Each chain consists of five domains, the third of which is an eight-stranded alpha/beta barrel that comprises much of the active site. This site does, however, include elements from other domains and other subunits. The N-terminal region of the polypeptide chains help form one of the subunit interfaces. Taken together these features provide a structural basis for the well-known property of alpha-complementation. Catalytic activity proceeds via the formation of a covalent galactosyl intermediate with Glu537, and includes 'shallow' and 'deep' modes of substrate binding.