An inhibitor/anti-inhibitor system controls the activity of lytic transglycosylase MltF in Pseudomonas aeruginosa.
An inhibitor/anti-inhibitor system controls the activity of lytic transglycosylase MltF in Pseudomonas aeruginosa.
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大多数细菌的细胞膜都含有一层由肽聚糖构成的细胞壁。新肽聚糖的合成对细胞生长、分裂和形态发生至关重要，并且还与肽聚糖水解协调以容纳新物质。然而，切割肽聚糖的酶必须小心控制，以避免自溶。近年来，一些控制机制已经开始出现，尽管对于大多数细胞壁水解酶是如何被调节的，还有更多的问题。在这里，我们报告了铜绿假单胞菌细胞壁水解酶的一种新的控制机制，这是我们在对分泌素蛋白过量产生敏感的突变体进行表征时发现的。该突变影响了PA3978位点编码的一个未表征的sel1样重复蛋白。除了分泌素敏感性表型外，PA3978破坏还增加了对临床使用的β-内酰胺类抗生素的耐药性。体内和体外分析表明，PA3978结合到裂解转糖基化酶MltF的催化结构域并抑制其活性。∆PA3978突变型通过删除mltF被抑制，这与mltF活性升高引起的表型一致。我们还发现了PA5502位点编码的PA3978的另一个互作伙伴。(1) PA5502突变体的表型表明，PA5502干扰了PA3978对MltF的抑制功能，并在体外证实了PA5502对MltF的抑制作用。因此，PA3978和PA5502形成了控制MltF活性的抑制剂/抗抑制剂体系。我们建议将这些蛋白命名为IltA（裂解转糖基酶抑制剂A）和LiiA（裂解转糖基酶抑制剂A的抑制剂）。肽聚糖细胞壁是几乎所有细菌细胞包膜的重要组成部分，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治疗细菌感染最重要的方法之一。肽聚糖也必须水解，以纳入细胞生长和分裂的新材料，并帮助适应重要的包膜跨越系统。然而，水解肽聚糖的酶必须小心控制，以防止自溶。在大多数情况下，这种控制究竟是如何实现的，人们知之甚少，但这是当前研究的一个高度活跃的领域。确定水解酶的控制机制有可能为治疗干预提供新的靶点。这项工作报告了一种新的抑制剂/抗抑制剂系统的重要发现，该系统控制人类病原体铜绿假单胞菌细胞壁水解酶的活性，这也影响对临床使用的抗生素的耐药性。
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 Pseudomonas aeruginosa, 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. In vivo and in vitro analyses revealed that PA3978 binds to the catalytic domain of the lytic transglycosylase MltF and inhibits its activity. ∆PA3978 mutant phenotypes were suppressed by deleting mltF, 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 ∆PA5502 mutant suggested that PA5502 interferes with the inhibitory function of PA3978 toward MltF, and we confirmed that activity for PA5502 in vitro. Therefore, PA3978 and PA5502 form an inhibitor/anti-inhibitor system that controls MltF activity. We propose to name these proteins IltA (inhibitor A of lytic transglycosylase) and LiiA (lytic transglycosylase inhibitor A’s 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-inhibitor system that controls the activity of a cell wall hydrolase in the human pathogen Pseudomonas aeruginosa, which also affects resistance to an antibiotic used in the clinic.
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