A Proteolytic Complex Targets Multiple Cell Wall Hydrolases in Pseudomonas aeruginosa.
A Proteolytic Complex Targets Multiple Cell Wall Hydrolases in Pseudomonas aeruginosa.
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DOI：
10.1128/mbio.00972-18
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发表时间：
2018-07-17
期刊：
影响因子：
6.4
通讯作者：
Darwin AJ
中科院分区：
文献类型：
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作者：
Srivastava D;Seo J;Rimal B;Kim SJ;Zhen S;Darwin AJ
羧基末端加工蛋白酶（CTP）存在于生命的所有三个领域。在细菌中，其中一些与毒性有关。然而，人们对细菌CTP的确切作用知之甚少，并且几乎没有发现直接的蛋白水解底物。一种细菌CTP是铜绿假单胞菌的CtpA蛋白酶，其是急性肺炎小鼠模型中III型分泌系统（T3 SS）功能和毒力所需的。在这里，我们研究了CtpA在铜绿假单胞菌中的功能，并鉴定了它切割的一些蛋白质。我们发现CtpA与一种以前未表征的蛋白质形成复合物，我们将其命名为LbcA（CtpA的脂蛋白结合伴侣）。LbcA是体内CtpA活性所必需的，并在体外促进其活性。我们还确定了四个蛋白水解底物的CtpA，所有这些都是未知的蛋白质预测切割肽聚糖内的肽交联。与此相一致，发现ctpA无效突变体具有比野生型更少的肽聚糖交联，并且在无盐培养基中生长缓慢。有趣的是，一些ΔctpA突变体表型（包括缺陷型T3 SS）仅需要一种CtpA底物的积累。我们认为LbcA-CtpA是铜绿假单胞菌细胞膜中的蛋白水解复合物，其通过降解肽聚糖交联水解酶来控制肽聚糖交联水解酶的活性。此外，基于这些和其他研究结果，我们认为，许多细菌CTP可能类似地由伴侣蛋白控制，作为控制肽聚糖水解酶活性的广泛机制的一部分。细菌羧基末端加工蛋白酶（CTP）是一种广泛保守的蛋白酶，与多种细菌的毒力有关。然而，它们的作用知之甚少，在任何物种中几乎没有发现直接底物。铜绿假单胞菌是一种重要的人类病原体，其中一种CTP，称为CtpA，是III型分泌系统功能和毒力所必需的。这项工作提供了一个重要的进展，显示CtpA工程与以前未表征的结合伙伴降解四个基板。这些底物都预测水解肽聚糖交联，表明CtpA复合物是肽聚糖水解的重要控制机制。这很可能成为一种广泛的机制，由不同的细菌控制它们的一些肽聚糖水解酶。鉴于CTP与几种病原体中的毒力之间的联系以及肽聚糖重塑对几乎所有细菌细胞的重要性，这是重要的。
Carboxy-terminal processing proteases (CTPs) occur in all three domains of life. In bacteria, some of them have been associated with virulence. However, the precise roles of bacterial CTPs are poorly understood, and few direct proteolytic substrates have been identified. One bacterial CTP is the CtpA protease of Pseudomonas aeruginosa, which is required for type III secretion system (T3SS) function and for virulence in a mouse model of acute pneumonia. Here, we have investigated the function of CtpA in P. aeruginosa and identified some of the proteins it cleaves. We discovered that CtpA forms a complex with a previously uncharacterized protein, which we have named LbcA (lipoprotein binding partner of CtpA). LbcA is required for CtpA activity in vivo and promotes its activity in vitro. We have also identified four proteolytic substrates of CtpA, all of which are uncharacterized proteins predicted to cleave the peptide cross-links within peptidoglycan. Consistent with this, a ctpA null mutant was found to have fewer peptidoglycan cross-links than the wild type and grew slowly in salt-free medium. Intriguingly, the accumulation of just one of the CtpA substrates was required for some ΔctpA mutant phenotypes, including the defective T3SS. We propose that LbcA-CtpA is a proteolytic complex in the P. aeruginosa cell envelope, which controls the activity of several peptidoglycan cross-link hydrolases by degrading them. Furthermore, based on these and other findings, we suggest that many bacterial CTPs might be similarly controlled by partner proteins as part of a widespread mechanism to control peptidoglycan hydrolase activity. Bacterial carboxy-terminal processing proteases (CTPs) are widely conserved and have been associated with the virulence of several species. However, their roles are poorly understood, and few direct substrates have been identified in any species. Pseudomonas aeruginosa is an important human pathogen in which one CTP, known as CtpA, is required for type III secretion system function and for virulence. This work provides an important advance by showing that CtpA works with a previously uncharacterized binding partner to degrade four substrates. These substrates are all predicted to hydrolyze peptidoglycan cross-links, suggesting that the CtpA complex is an important control mechanism for peptidoglycan hydrolysis. This is likely to emerge as a widespread mechanism used by diverse bacteria to control some of their peptidoglycan hydrolases. This is significant, given the links between CTPs and virulence in several pathogens and the importance of peptidoglycan remodeling to almost all bacterial cells.