Crystal structure of PBP2x from a highly penicillin-resistant Streptococcus pneumoniae clinical isolate - A mosaic framework containing 83 mutations
Crystal structure of PBP2x from a highly penicillin-resistant Streptococcus pneumoniae clinical isolate - A mosaic framework containing 83 mutations
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DOI：
10.1074/jbc.m107608200
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发表时间：
2001-11-30
影响因子：
4.8
通讯作者：
Dideberg, O
中科院分区：
文献类型：
--
作者：
Dessen, A;Mouz, N;Dideberg, O
青霉素结合蛋白(PBPs)是β-内酰胺类抗生素的主要靶标，如青霉素类和头孢菌素类，存在于多种细菌中。在一些革兰氏阳性菌株中，对β-内酰胺类药物治疗的耐药性激增主要是由于嵌合体PBP编码基因的增殖，这些基因通过重组编码新的蛋白质。PBP2x是肺炎链球菌的主要耐药决定基因，其修饰是发展高水平β-内酰胺类耐药的关键步骤。为了在原子水平上了解这种耐药机制，我们从高度耐青霉素的肺炎链球菌临床分离株Sp328中解析了PBP2x的X射线晶体结构，该菌株在可溶区含有83个突变。在Sp328PBP2x*活性中心附近，Thr(338)-->；Ala突变削弱了局部氢键网络，从而破坏了一个关键的潜水分子的稳定性。此外，Ser(389)-->；Leu和Asn(514)-->；他的突变会产生一种不稳定的效应，产生一个“开放”的活性位点。已有研究表明，对β-内酰胺耐药的PBPs的肽聚糖底物含有大量异常的支链多肽，而敏感菌株倾向于催化线性形式的交联。因此，在体内，一个“开放”的活性部位可以促进识别不同的、分支的生理底物。
Penicillin-binding proteins (PBPs) are the main targets for beta -lactam antibiotics, such as penicillins and cephalosporins, in a wide range of bacterial species. In some Gram-positive strains, the surge of resistance to treatment with beta -lactams is primarily the result of the proliferation of mosaic PBP-encoding genes, which encode novel proteins by recombination. PBP2x is a primary resistance determinant in Streptococcus pneumoniae, and its modification is an essential step in the development of high level beta -lactam resistance. To understand such a resistance mechanism at an atomic level, we have solved the x-ray crystal structure of PBP2x from a highly penicillin-resistant clinical isolate of S. pneumoniae, Sp328, which harbors 83 mutations in the soluble region. In the proximity of the Sp328 PBP2x* active site, the Thr(338)--> Ala mutation weakens the local hydrogen bonding network, thus abrogating the stabilization of a crucial buried water molecule. In addition, the Ser(389)--> Leu and Asn(514)--> His mutations produce a destabilizing effect that generates an "open" active site. It has been suggested that peptidoglycan substrates for beta -lactam-resistant PBPs contain a large amount of abnormal, branched peptides, whereas sensitive strains tend to catalyze cross-linking of linear forms. Thus, in vivo, an "open" active site could facilitate the recognition of distinct, branched physiological substrates.