Crystal Structures of Pseudomonas aeruginosa GIM-1: Active-Site Plasticity in Metallo-β-Lactamases
Crystal Structures of Pseudomonas aeruginosa GIM-1: Active-Site Plasticity in Metallo-β-Lactamases
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DOI：
10.1128/aac.02227-12
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发表时间：
2013-02-01
影响因子：
4.9
通讯作者：
Leiros, Hanna-Kirsti S.
中科院分区：
文献类型：
--
作者：
Borra, Pardha Saradhi;Samuelsen, Orjan;Leiros, Hanna-Kirsti S.
金属β-内酰胺酶（MBL）在临床上重要的革兰氏阴性菌中迅速传播，并对β-内酰胺抗生素（特别是碳青霉烯类）的治疗用途提出了挑战。bla（GIM-1）基因，编码一种这样的酶，首次发现于2002年的铜绿假单胞菌分离株，最近在肠杆菌科中有报道。在这里，我们呈现了GIM-1的脱辅基锌（无金属），单锌（发现Cys 221被氧化）和二锌形式的晶体结构，提供了九个独立的酶的精细视图。GIM-1与相关MBL的不同之处在于，在其他MBL中通常由亲水残基占据的位置处具有由芳香族侧链（Trp 228和Tyr 233）限定的较窄的活性位点凹槽。我们的结构揭示了相当大的灵活性，在两个环（环1，残基60至66;环2，残基223至242）相邻的活性位点，与开放和封闭的构象所定义的替代氢键模式，涉及Trp 228。我们认为，这种能力的重排允许GIM-1水解广泛的β-内酰胺，尽管拥有一个更受限制的活性位点。我们的研究结果突出了MBL酶家族内的结构多样性。
Metallo-beta-lactamases (MBLs) have rapidly disseminated worldwide among clinically important Gram-negative bacteria and have challenged the therapeutic use of beta-lactam antibiotics, particularly carbapenems. The bla(GIM-1) gene, encoding one such enzyme, was first discovered in a Pseudomonas aeruginosa isolate from 2002 and has more recently been reported in Enterobacteriaceae. Here, we present crystal structures of GIM-1 in the apo-zinc (metal-free), mono-zinc (where Cys221 was found to be oxidized), and di-zinc forms, providing nine independently refined views of the enzyme. GIM-1 is distinguished from related MBLs in possessing a narrower active-site groove defined by aromatic side chains (Trp228 and Tyr233) at positions normally occupied by hydrophilic residues in other MBLs. Our structures reveal considerable flexibility in two loops (loop 1, residues 60 to 66; loop 2, residues 223 to 242) adjacent to the active site, with open and closed conformations defined by alternative hydrogen-bonding patterns involving Trp228. We suggest that this capacity for rearrangement permits GIM-1 to hydrolyze a wide range of beta-lactams in spite of possessing a more constrained active site. Our results highlight the structural diversity within the MBL enzyme family.