Carnevale Matías C, Palacios Antonela R, Hinchliffe Philip, Delmonti Juliana, Drusin Salvador I, Moreno Diego M, Bonomo Robert A, Spencer James, Vila Alejandro J
Laboratorio de Metaloproteínas, Instituto de Biologia Molecular y Celular de Rosario (IBR, CONICET-UNR), Rosario, Argentina.
School of Cellular and Molecular Medicine, University of Bristol, Bristol, United Kingdom.
Antimicrob Agents Chemother. 2025 Jun 23:e0191824. doi: 10.1128/aac.01918-24.
Antimicrobial resistance is a significant global public health threat that limits treatment options for bacterial infections. This situation is aggravated by the environmental spread of β-lactamase genes. In particular, metallo-β-lactamases (MBLs) hydrolyze almost all available β-lactam antibiotics, including late-generation cephalosporins and carbapenems. Among MBLs, the New Delhi metallo-β-lactamase (NDM-1) of subclass B1 has shown the most ominous dissemination. NDM variants are the only MBLs of clinical importance that are membrane-anchored, a sub-cellular localization that endows them with high stability under conditions of metal limitation. However, antibiotic resistance predates modern antibiotic usage, and environmental bacteria serve as reservoirs for resistance genes. Here, we report the biochemical and structural characterization of two membrane-bound MBLs: CJO-1 and CIM-2, from and , respectively. Both MBLs confer β-lactam resistance on producer bacterial strains and hydrolyze several antibiotics, although with impaired efficiency compared to NDM-1. Crystal structures reveal differences, compared to previously studied B1 MBLs, in the active site loops and their dynamic properties that impact activity. Specifically, a hindered access to the active site with the contribution of a Tyr residue in loop L10 and the presence of a positively charged Lys residue in loop L3 limit hydrolysis of cephalosporins with charged C3 substituents. Some of these novel features are preserved in other MBLs from spp. These findings suggest that spp. could act as reservoirs of MBL genes, while informing on the diversity of structure-function relationships and dynamic behaviors within the B1 subclass of these enzymes.
抗菌药物耐药性是一个重大的全球公共卫生威胁，它限制了细菌感染的治疗选择。β-内酰胺酶基因在环境中的传播加剧了这种情况。特别是金属β-内酰胺酶（MBLs）几乎能水解所有可用的β-内酰胺抗生素，包括新一代头孢菌素和碳青霉烯类。在MBLs中，B1亚类的新德里金属β-内酰胺酶（NDM-1）显示出最不祥的传播态势。NDM变体是仅有的具有临床重要性的膜锚定MBLs，这种亚细胞定位使其在金属限制条件下具有高稳定性。然而，抗生素耐药性在现代抗生素使用之前就已存在，环境细菌是耐药基因的储存库。在此，我们报告了分别来自[具体来源1]和[具体来源2]的两种膜结合MBLs：CJO-1和CIM-2的生化和结构特征。两种MBLs都赋予产生菌菌株β-内酰胺抗性并能水解多种抗生素，尽管与NDM-1相比效率有所受损。晶体结构显示，与先前研究的B1 MBLs相比，活性位点环及其影响活性的动态特性存在差异。具体而言，L10环中一个酪氨酸残基的作用导致活性位点的可及性受阻，以及L3环中一个带正电的赖氨酸残基的存在限制了带有带电荷C3取代基的头孢菌素的水解。这些新特征中的一些在来自[具体物种]的其他MBLs中也有保留。这些发现表明[具体物种]可能是MBL基因的储存库，同时也为这些酶的B1亚类内结构-功能关系和动态行为的多样性提供了信息。
