Structure-function relationships among wild-type variants of Staphylococcus aureus beta-lactamase: importance of amino acids 128 and 216.
Structure-function relationships among wild-type variants of Staphylococcus aureus beta-lactamase: importance of amino acids 128 and 216.
复制标题
金黄色葡萄球菌 β-内酰胺酶野生型变体之间的结构-功能关系：氨基酸 128 和 216 的重要性。
DOI：
10.1128/jb.178.24.7248-7253.1996
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发表时间：
1996
影响因子：
3.2
通讯作者：
Kernodle,DS
中科院分区：
文献类型：
--
作者：
Voladri,RK;Tummuru,MK;Kernodle,DS
beta-Lactamases inactivate penicillin and cephalosporin antibiotics by hydrolysis of the beta-lactam ring and are an important mechanism of resistance for many bacterial pathogens. Four wild-type variants of Staphylococcus aureus beta-lactamase, designated A, B, C, and D, have been identified. Although distinguishable kinetically, they differ in primary structure by only a few amino acids. Using the reported sequences of the A, C, and D enzymes along with crystallographic data about the structure of the type A enzyme to identify amino acid differences located close to the active site, we hypothesized that these differences might explain the kinetic heterogeneity of the wild-type beta-lactamases. To test this hypothesis, genes encoding the type A, C, and D beta-lactamases were modified by site-directed mutagenesis, yielding mutant enzymes with single amino acid substitutions. The substitution of asparagine for serine at residue 216 of type A beta-lactamase resulted in a kinetic profile indistinguishable from that of type C beta-lactamase, whereas the substitution of serine for asparagine at the same site in the type C enzyme produced a kinetic type A mutant. Similar bidirectional substitutions identified the threonine-to-alanine difference at residue 128 as being responsible for the kinetic differences between the type A and D enzymes. Neither residue 216 nor 128 has previously been shown to be kinetically important among serine-active-site beta-lactamases.
