Wang Michelle, Ma Sheya Xiao, Darwin Andrew J
bioRxiv. 2023 Jul 28:2023.07.28.551027. doi: 10.1101/2023.07.28.551027.
Most bacterial cell envelopes contain a cell wall layer made of peptidoglycan. The synthesis of new peptidoglycan is critical for cell growth, division and morphogenesis, and is also coordinated with peptidoglycan hydrolysis to accommodate the new material. However, the enzymes that cleave peptidoglycan must be carefully controlled to avoid autolysis. In recent years, some control mechanisms have begun to emerge, although there are many more questions than answers for how most cell wall hydrolases are regulated. Here, we report a novel cell wall hydrolase control mechanism in , which we discovered during our characterization of a mutant sensitive to the overproduction of a secretin protein. The mutation affected an uncharacterized Sel1-like repeat protein encoded by the PA3978 locus. In addition to the secretin-sensitivity phenotype, PA3978 disruption also increased resistance to a β-lactam antibiotic used in the clinic. and analysis revealed that PA3978 binds to the catalytic domain of the lytic transglycosylase MltF and inhibits its activity. ΔPA3978 mutant phenotypes were suppressed by deleting , consistent with them having been caused by elevated MltF activity. We also discovered another interaction partner of PA3978 encoded by the PA5502 locus. The phenotypes of a ΔPA5502 mutant suggested that PA5502 interferes with the inhibitory function of PA3978 towards MltF, and we confirmed that activity for PA5502 . Therefore, PA3978 and PA5502 form an inhibitor/anti-inhibitor system that controls MltF activity. We propose to name these proteins Ilt (inhibitor of lytic transglycosylase) and Lii (lytic transglycosylase inhibitor, inhibitor).
A peptidoglycan cell wall is an essential component of almost all bacterial cell envelopes, which determines cell shape and prevents osmotic rupture. Antibiotics that interfere with peptidoglycan synthesis have been one of the most important treatments for bacterial infections. Peptidoglycan must also be hydrolyzed to incorporate new material for cell growth and division, and to help accommodate important envelope-spanning systems. However, the enzymes that hydrolyze peptidoglycan must be carefully controlled to prevent autolysis. Exactly how this control is achieved is poorly understood in most cases, but is a highly active area of current research. Identifying hydrolase control mechanisms has the potential to provide new targets for therapeutic intervention. The work here reports the important discovery of a novel inhibitor/anti-nhibitor system that controls the activity of a cell wall hydrolase in the human pathogen , and which also affects resistance to an antibiotic used in the clinic.
大多数细菌细胞壁包含一层由肽聚糖构成的细胞壁层。新肽聚糖的合成对于细胞生长、分裂和形态发生至关重要，并且还与肽聚糖水解相协调以容纳新物质。然而，切割肽聚糖的酶必须受到严格控制以避免自溶。近年来，一些控制机制已开始显现，尽管对于大多数细胞壁水解酶如何被调节，问题远多于答案。在此，我们报告了一种新的细胞壁水解酶控制机制，这是我们在对一种对分泌素蛋白过量产生敏感的突变体进行表征过程中发现的。该突变影响了由PA3978基因座编码的一种未表征的类Sel1重复蛋白。除了分泌素敏感表型外，PA3978基因的破坏还增加了对临床使用的一种β-内酰胺抗生素的抗性。[具体实验名称]分析表明，PA3978与溶菌转糖基酶MltF的催化结构域结合并抑制其活性。通过缺失[相关基因]抑制了ΔPA3978突变体表型，这与它们是由MltF活性升高引起的一致。我们还发现了由PA5502基因座编码的PA3978的另一个相互作用伙伴。ΔPA5502突变体的表型表明PA5502干扰了PA3978对MltF的抑制功能，并且我们证实了PA5502的活性。因此，PA3978和PA5502形成了一个控制MltF活性的抑制剂/抗抑制剂系统。我们提议将这些蛋白质命名为Ilt（溶菌转糖基酶抑制剂）和Lii（溶菌转糖基酶抑制剂的抑制剂）。
肽聚糖细胞壁是几乎所有细菌细胞壁的重要组成部分，它决定细胞形状并防止渗透破裂。干扰肽聚糖合成的抗生素一直是细菌感染最重要的治疗方法之一。肽聚糖也必须被水解以纳入用于细胞生长和分裂的新物质，并有助于容纳重要的跨膜系统。然而，水解肽聚糖的酶必须受到严格控制以防止自溶。在大多数情况下，究竟如何实现这种控制尚不清楚，但这是当前研究的一个高度活跃领域。确定水解酶控制机制有可能为治疗干预提供新的靶点。本文的工作报道了一个重要发现，即一种新的抑制剂/抗抑制剂系统控制了人类病原体[具体病原体名称]中一种细胞壁水解酶的活性，并且这也影响了对临床使用的一种抗生素的抗性。
