PHOP-REG SALMONELLA RESISTANCE TO ANTIMICR PEPTIDES MAGAININ 2 AND POLYMYXIN B

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。在肠沙门氏菌中，PhoP PhoQ双组分系统控制着对结构不同的抗菌肽的抗性，包括α -螺旋magainin 2、-sheet防御素和环脂肽多粘菌素b。为了鉴定PhoP调控的决定因素介导肽抗性，我们从PhoP突变体中制备了一个质粒文库，将其引入PhoP突变体并选择耐magainin克隆。其中一个克隆含有phop激活的ugtL基因，该基因的缺失使沙门氏菌对magainin2和多粘菌素B敏感，但对防御蛋白HNP-1不敏感。我们确定ugtL编码一种内膜蛋白，该蛋白促进脂多糖中单磷酸化脂质A的形成。ugtL和调控基因pmrA失活导致菌株与PhoP突变体一样对多粘菌素B敏感。pmrA控制脂质A修饰，对多粘菌素B具有抗性（但不抵抗magainin 2），并被PhoP PhoQ系统转录后激活。最常见的克隆含有yqjA基因，我们发现它是PhoP调控的，是抵抗magainin 2而不是抵抗多粘菌素B或防御蛋白HNP-1所必需的。我们的研究结果表明，磷脂介导的脂质A的不同修饰是对不同抗菌肽的抗性所必需的。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In Salmonella enterica, the PhoP PhoQ two-component system governs resistance to structurally different antimicrobial peptides including the alpha-helical magainin 2, the -sheet defensins and the cyclic lipopeptide polymyxin B. To identify the PhoP-regulated determinants mediating peptide resistance, we prepared a plasmid library from a phoP mutant, introduced it into a phoP mutant and selected for magainin-resistant clones. One of the clones harboured the PhoP-activated ugtL gene, deletion of which rendered Salmonella susceptible to magainin 2 and polymyxin B, but not defensin HNP-1. We established that ugtL encodes an inner membrane protein that promotes the formation of monophosphorylated lipid A in the lipopolysaccharide. Inactivation of both ugtL and the regulatory gene pmrA, which controls lipid A modifications required for resistance to polymxyin B (but not to magainin 2) and is post-transcriptionally activated by the PhoP PhoQ system, resulted in a strain that was as susceptible to polymyxin B as a phoP mutant. The most frequently recovered clone harboured the yqjA gene, which we show is PhoP regulated and required for resistance to magainin 2 but not to polymyxin B or defensin HNP-1. Our results indicate that different PhoP-mediated modifications in lipid A are necessary for resistance to different antimicrobial peptides.