Crystal Structure of Serratia fonticola Sfh-I: Activation of the Nucleophile in Mono-Zinc Metallo-β-Lactamases
Crystal Structure of Serratia fonticola Sfh-I: Activation of the Nucleophile in Mono-Zinc Metallo-β-Lactamases
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DOI：
10.1016/j.jmb.2011.06.043
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发表时间：
2011-09-02
影响因子：
5.6
通讯作者：
Spencer, James
中科院分区：
文献类型：
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作者：
Fonseca, Fatima;Bromley, Elizabeth H. C.;Spencer, James
金属β-内酰胺酶(MBLS)或B类β-内酰胺酶是一种依赖锌的酶，几乎能灭活所有种类的β-内酰胺类抗生素。到目前为止，还没有MBL抑制剂可用于临床。在三个MBL亚类中，B2酶不同于B1和B3亚类的酶，它只与一个锌离子结合，具有完全的活性，并且活性谱很窄，几乎只水解碳青霉烯类底物。这些仍然是研究最少的MBLs。SFH-I最初是从水生细菌沙雷氏菌UTAD54中鉴定出来的，是这一组中的一个不同成员。以前的B2 MBL结构只适用于嗜水气单胞菌的CPHA酶，都含有结合在活性部位的小分子。因此，这些酶激活β-内酰胺水解所需的水亲核试剂的机制仍有待明确确立。在这里，我们报道了SFH-I的晶体结构，它是一种与甘油形成的未连接形式的络合物，首次揭示了水分子在B2 MBL活性中心的配置。我们的数据表明水解水分子是被His118激活的，而不是被Asp120和/或锌激活的。与这一建议一致，我们证明了B2MBLS中His118的环境不同于B1和B3酶的环境，在B1和B3酶中，该残基充当锌配体，并为这些酶对p-内酰胺的水解提供了一种基于结构的机制。(C)2011爱思唯尔有限公司。保留所有权利。
Metallo-p,-lactamases (MBLs) or class B beta-lactamases are zinc-dependent enzymes capable of inactivating almost all classes of beta-lactam antibiotics. To date, no MBL inhibitors are available for clinical use. Of the three MBL subclasses, B2 enzymes, unlike those from subclasses B1 and B3, are fully active with one zinc ion bound and possess a narrow spectrum of activity, hydrolyzing carbapenem substrates almost exclusively. These remain the least studied MBLs. Sfh-I, originally identified from the aquatic bacterium Serratia fonticola UTAD54, is a divergent member of this group. Previous B2 MBL structures, available only for the CphA enzyme from Aeromonas hydrophila, all contain small molecules bound in their active sites. In consequence, the mechanism by which these enzymes activate the water nucleophile required for beta-lactam hydrolysis remains to be unambiguously established. Here we report crystal structures of Sfh-I as a complex with glycerol and in the unliganded form, revealing for the first time the disposition of water molecules in the B2 MBL active site. Our data indicate that the hydrolytic water molecule is activated by His118 rather than by Asp120 and/or zinc. Consistent with this proposal, we show that the environment of His118 in B2 MBLs is distinct from that of the B1 and B3 enzymes, where this residue acts as a zinc ligand, and offer a structure-based mechanism for p-lactam hydrolysis by these enzymes. (C) 2011 Elsevier Ltd. All rights reserved.