Department of Microbiology and Immunology, Center for Infectious Disease Research, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
Antimicrob Agents Chemother. 2024 Sep 4;68(9):e0055524. doi: 10.1128/aac.00555-24. Epub 2024 Jul 26.
Enterococci exhibit intrinsic resistance to cephalosporins, mediated in part by the class B penicillin-binding protein (bPBP) Pbp4 that exhibits low reactivity toward cephalosporins and thus can continue crosslinking peptidoglycan despite exposure to cephalosporins. bPBPs partner with cognate SEDS (shape, elongation, division, and sporulation) glycosyltransferases to form the core catalytic complex of peptidoglycan synthases that synthesize peptidoglycan at discrete cellular locations, although the SEDS partner for Pbp4 is unknown. SEDS-bPBP peptidoglycan synthases of enterococci have not been studied, but some SEDS-bPBP pairs can be predicted based on sequence similarity. For example, FtsW (SEDS)-PbpB (bPBP) is predicted to form the catalytic core of the peptidoglycan synthase that functions at the division septum (the divisome). However, PbpB is readily inactivated by cephalosporins, raising the question-how could the FtsW-PbpB synthase continue functioning to enable growth in the presence of cephalosporins? In this work, we report that the FtsW-PbpB peptidoglycan synthase is required for cephalosporin resistance of , despite the fact that PbpB is inactivated by cephalosporins. Moreover, Pbp4 associates with the FtsW-PbpB synthase and the TPase activity of Pbp4 is required to enable growth in the presence of cephalosporins in an FtsW-PbpB-synthase-dependent manner. Overall, our results implicate a model in which Pbp4 directly interacts with the FtsW-PbpB peptidoglycan synthase to provide TPase activity during cephalosporin treatment, thereby maintaining the divisome SEDS-bPBP peptidoglycan synthase in a functional state competent to synthesize crosslinked peptidoglycan. These results suggest that two bPBPs coordinate within the FtsW-PbpB peptidoglycan synthase to drive cephalosporin resistance in .
肠球菌对头孢菌素表现出固有耐药性，部分由 B 类青霉素结合蛋白（bPBP）Pbp4 介导，该蛋白对头孢菌素的反应性较低，因此尽管暴露于头孢菌素中，仍能继续交联肽聚糖。bPBPs 与同源的 SEDS（形状、伸长、分裂和孢子形成）糖基转移酶形成肽聚糖合酶的核心催化复合物，在离散的细胞位置合成肽聚糖，尽管 Pbp4 的 SEDS 伴侣尚不清楚。肠球菌的 SEDS-bPBP 肽聚糖合酶尚未被研究，但可以根据序列相似性预测一些 SEDS-bPBP 对。例如，FtsW（SEDS）-PbpB（bPBP）被预测形成在分裂隔膜（分裂体）处起作用的肽聚糖合酶的催化核心。然而，PbpB 很容易被头孢菌素失活，这就提出了一个问题——在头孢菌素存在的情况下，FtsW-PbpB 合酶如何继续发挥作用以促进生长？在这项工作中，我们报告说，尽管 PbpB 被头孢菌素失活，但 FtsW-PbpB 肽聚糖合酶是 对头孢菌素耐药所必需的。此外，Pbp4 与 FtsW-PbpB 合酶结合，并且 Pbp4 的 TPase 活性是在 FtsW-PbpB-合酶依赖性方式下在头孢菌素存在下生长所必需的。总体而言，我们的结果表明，Pbp4 直接与 FtsW-PbpB 肽聚糖合酶相互作用，在头孢菌素处理期间提供 TPase 活性，从而使分裂体 SEDS-bPBP 肽聚糖合酶保持交联肽聚糖合成的功能状态。这些结果表明，两个 bPBPs 在 FtsW-PbpB 肽聚糖合酶内协调，以驱动 对头孢菌素的耐药性。
