Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center , University of Oklahoma , 101 Stephenson Parkway , Norman , Oklahoma 73019 , United States.
Laboratory of Bacterial Cell Biology, Instituto de Tecnologia Química e Biologica António Xavier , Universidade NOVA de Lisboa , Av. da República , 2780-157 Oeiras , Portugal.
Biochemistry. 2019 Sep 10;58(36):3813-3822. doi: 10.1021/acs.biochem.9b00523. Epub 2019 Aug 26.
With its high morbidity rate and increasing resistance to treatment, methicillin-resistant (MRSA) is a grave concern in the medical field. In methicillin-susceptible strains, β-lactam antibiotics disable the penicillin binding proteins (PBPs) that cross-link the bacterial cell wall. However, methicillin-resistant strains have PBP2a and PBP4, which continue enzymatic activity in the presence of β-lactam antibiotics. The activity of PBP2a and PBP4 is linked to the presence of wall teichoic acid (WTA); thus, WTA has emerged as a target for antibiotic drug discovery. In this work, we disable WTA using its anionic phosphodiester backbone to attract cationic branched polyethylenimine (BPEI). Data show that BPEI removes β-lactam resistance in common MRSA strains and clinical isolates. Fluorescence microscopy was used to investigate this mechanism of action. The results indicate that BPEI prevents the localization of PBP4 to the cell division septum, thereby changing the cellular morphology and inhibiting cell division. Although PBP4 is not required for septum formation, proper cell division and morphology require WTA; BPEI prevents this essential function. The combination of BPEI and β-lactams is bactericidal and synergistic. Because BPEI allows us to study the role of WTA in the cell wall without genetic mutation or altered translocation of biomolecules and/or their precursors, this approach can help revise existing paradigms regarding the role of WTA in prokaryotic biochemistry at every growth stage.
耐甲氧西林金黄色葡萄球菌（MRSA）具有较高的发病率和不断增加的治疗耐药性，这是医学界关注的一个严重问题。在甲氧西林敏感菌株中，β-内酰胺类抗生素使青霉素结合蛋白（PBPs）失活，这些蛋白交联细菌细胞壁。然而，耐甲氧西林的菌株具有 PBP2a 和 PBP4，它们在β-内酰胺类抗生素存在的情况下继续进行酶促活性。PBP2a 和 PBP4 的活性与壁磷壁酸（WTA）的存在有关；因此，WTA 已成为抗生素药物发现的靶点。在这项工作中，我们使用 WTA 的阴离子磷酸二酯骨架来吸引阳离子支化聚乙烯亚胺（BPEI），从而使 WTA 失活。数据表明，BPEI 可去除常见 MRSA 菌株和临床分离株中的β-内酰胺耐药性。荧光显微镜用于研究这种作用机制。结果表明，BPEI 阻止 PBP4 定位到细胞分裂隔膜，从而改变细胞形态并抑制细胞分裂。尽管 PBP4 不是隔膜形成所必需的，但适当的细胞分裂和形态需要 WTA；BPEI 阻止了这种必需的功能。BPEI 和β-内酰胺类药物的联合使用具有杀菌和协同作用。由于 BPEI 使我们能够在不进行遗传突变或改变生物分子及其前体的易位的情况下研究 WTA 在细胞壁中的作用，因此这种方法有助于修订关于 WTA 在每个生长阶段的原核生物化学中的作用的现有范式。
