Figueroa-Cuilan Wanda M, Randich Amelia M, Dunn Caroline M, Santiago-Collazo Gustavo, Yowell Andrew, Brown Pamela J B
Division of Biological Sciences, University of Missouri, Columbia, MO, United States.
Department of Biology, University of Scranton, Scranton, PA, United States.
Front Microbiol. 2021 Aug 18;12:729307. doi: 10.3389/fmicb.2021.729307. eCollection 2021.
LytM-domain containing proteins are LAS peptidases (lysostaphin-type enzymes, D-Ala-D-Ala metallopeptidases, and sonic hedgehog) and are known to play diverse roles throughout the bacterial cell cycle through direct or indirect hydrolysis of the bacterial cell wall. A subset of the LytM factors are catalytically inactive but regulate the activity of other cell wall hydrolases and are classically described as cell separation factors NlpD and EnvC. Here, we explore the function of four LytM factors in the alphaproteobacterial plant pathogen . An LmdC ortholog (Atu1832) and a MepM ortholog (Atu4178) are predicted to be catalytically active. While Atu1832 does not have an obvious function in cell growth or division, Atu4178 is essential for polar growth and likely functions as a space-making endopeptidase that cleaves amide bonds in the peptidoglycan cell wall during elongation. The remaining LytM factors are degenerate EnvC and NlpD orthologs. Absence of these proteins results in striking phenotypes indicative of misregulation of cell division and growth pole establishment. The deletion of an amidase, AmiC, closely phenocopies the deletion of suggesting that EnvC might regulate AmiC activity. The NlpD ortholog DipM is unprecedently essential for viability and depletion results in the misregulation of early stages of cell division, contrasting with the canonical view of DipM as a cell separation factor. Finally, we make the surprising observation that absence of AmiC relieves the toxicity induced by overexpression. Together, these results suggest EnvC and DipM may function as regulatory hubs with multiple partners to promote proper cell division and establishment of polarity.
含LytM结构域的蛋白质是LAS肽酶（溶葡萄球菌素型酶、D-丙氨酰-D-丙氨酸金属肽酶和音猬因子），已知它们通过直接或间接水解细菌细胞壁在整个细菌细胞周期中发挥多种作用。一部分LytM因子催化无活性，但可调节其他细胞壁水解酶的活性，传统上被描述为细胞分离因子NlpD和EnvC。在此，我们探究了四种LytM因子在α变形菌属植物病原体中的功能。预测一个LmdC直系同源物（Atu1832）和一个MepM直系同源物（Atu4178）具有催化活性。虽然Atu1832在细胞生长或分裂中没有明显功能，但Atu4178对极性生长至关重要，可能作为一种在伸长过程中切割肽聚糖细胞壁中酰胺键的空间形成内肽酶发挥作用。其余的LytM因子是退化的EnvC和NlpD直系同源物。这些蛋白质的缺失导致了显著的表型，表明细胞分裂和生长极建立失调。酰胺酶AmiC的缺失与[缺失的蛋白]的缺失表现出相似的表型，这表明EnvC可能调节AmiC的活性。NlpD直系同源物DipM对生存力来说是前所未有的必需因子，其缺失导致细胞分裂早期阶段失调，这与将DipM视为细胞分离因子的传统观点形成对比。最后，我们有一个惊人的发现，即AmiC的缺失可减轻[蛋白]过表达诱导的毒性。总之，这些结果表明EnvC和DipM可能作为具有多个伙伴的调节枢纽，以促进正确的细胞分裂和极性建立。
