J Biochem. 2022 Jan 7;170(6):787-800. doi: 10.1093/jb/mvab102.
Acinetobacter baumannii is an insidious emerging nosocomial pathogen that has developed resistance to all available antimicrobials, including the last resort antibiotic, colistin. Colistin resistance often occurs due to mutations in the PmrAB two-component regulatory system. To better understand the regulatory mechanisms contributing to colistin resistance, we have biochemically characterized the A. baumannii PmrA response regulator. Initial DNA-binding analysis shows that A. baumannii PmrA bound to the Klebsiella pneumoniae PmrA box motif. This prompted analysis of the putative A. baumannii PmrAB regulon that indicated that the A. baumannii PmrA consensus box is 5'-HTTAAD N5 HTTAAD. Additionally, we provide the first structural information for the A. baumannii PmrA N-terminal domain through X-ray crystallography and we present a full-length model using molecular modelling. From these studies, we were able to infer the effects of two critical PmrA mutations, PmrA::I13M and PmrA::P102R, both of which confer increased colistin resistance. Based on these data, we suggest structural and dynamic reasons for how these mutations can affect PmrA function and hence encourage resistive traits. Understanding these mechanisms will aid in the development of new targeted antimicrobial therapies. Graphical Abstract.
鲍曼不动杆菌是一种具有潜在威胁的新兴医院病原体，已经对所有可用的抗菌药物产生了耐药性，包括最后的抗生素——多粘菌素。多粘菌素耐药性的产生通常是由于 PmrAB 双组分调控系统的突变。为了更好地了解导致多粘菌素耐药性的调控机制，我们对鲍曼不动杆菌 PmrA 反应调节剂进行了生化特性分析。初步的 DNA 结合分析表明，鲍曼不动杆菌 PmrA 与肺炎克雷伯氏菌 PmrA 盒基序结合。这促使我们对推定的鲍曼不动杆菌 PmrAB 调控组进行了分析，结果表明鲍曼不动杆菌 PmrA 共有盒基序为 5'-HTTAAD N5 HTTAAD。此外，我们通过 X 射线晶体学提供了鲍曼不动杆菌 PmrA N 端结构域的首个结构信息，并通过分子建模呈现了全长模型。通过这些研究，我们能够推断出两种关键的 PmrA 突变（PmrA::I13M 和 PmrA::P102R）的影响，这两种突变都导致了多粘菌素耐药性的增加。基于这些数据，我们提出了这些突变如何影响 PmrA 功能并因此鼓励耐药性特征的结构和动态原因。了解这些机制将有助于开发新的靶向抗菌治疗方法。
