Maréchal Maxime, Amoroso Ana, Morlot Cécile, Vernet Thierry, Coyette Jacques, Joris Bernard
Physiologie et génétique bactérienne, Centre d'Ingénierie des Protéines, Université de Liège, Institut de Chimie, Liège, B-4000, Belgium.
University Grenoble Alpes, IBS, Grenoble, F-38044, France.
BMC Microbiol. 2016 Oct 12;16(1):239. doi: 10.1186/s12866-016-0844-y.
Proteins from the LytR-CpsA-Psr family are found in almost all Gram-positive bacteria. Although LCP proteins have been studied in other pathogens, their functions in enterococci remain uncharacterized. The Psr protein from Enterococcus hirae, here renamed LcpA, previously associated with the regulation of the expression of the low-affinity PBP5 and β-lactam resistance, has been characterized.
LcpA protein of E. hirae ATCC 9790 has been produced and purified with and without its transmembrane helix. LcpA appears, through different methods, to be localized in the membrane, in agreement with in silico predictions. The interaction of LcpA with E. hirae cell wall indicates that LcpA binds enterococcal peptidoglycan, regardless of the presence of secondary cell wall polymers. Immunolocalization experiments showed that LcpA and PBP5 are localized at the division site of E. hirae.
LcpA belongs to the LytR-CpsA-Psr family. Its topology, localization and binding to peptidoglycan support, together with previous observations on defective mutants, that LcpA plays a role related to the cell wall metabolism, probably acting as a phosphotransferase catalyzing the attachment of cell wall polymers to the peptidoglycan.
LytR - CpsA - Psr家族的蛋白质几乎存在于所有革兰氏阳性细菌中。尽管LCP蛋白已在其他病原体中得到研究，但其在肠球菌中的功能仍未明确。来自平肠球菌的Psr蛋白，在此重新命名为LcpA，先前已被鉴定与低亲和力PBP5的表达调控及β - 内酰胺抗性有关。
已制备并纯化了平肠球菌ATCC 9790的LcpA蛋白，包括带有和不带有其跨膜螺旋的形式。通过不同方法，LcpA似乎定位于膜上，这与计算机模拟预测结果一致。LcpA与平肠球菌细胞壁的相互作用表明，无论次生细胞壁聚合物是否存在，LcpA都能结合肠球菌肽聚糖。免疫定位实验表明，LcpA和PBP5定位于平肠球菌的分裂位点。
LcpA属于LytR - CpsA - Psr家族。其拓扑结构、定位以及与肽聚糖的结合，再加上之前对缺陷突变体的观察结果，支持LcpA在细胞壁代谢中发挥作用，可能作为一种磷酸转移酶催化细胞壁聚合物与肽聚糖的连接。
