Shankar V, Baghdayan A S, Huycke M M, Lindahl G, Gilmore M S
Department of Medicinal Chemistry and Pharmaceutics, University of Oklahoma Health Sciences Center, Oklahoma City 73190, USA.
Infect Immun. 1999 Jan;67(1):193-200. doi: 10.1128/IAI.67.1.193-200.1999.
We report the identification of a new cell wall-associated protein of Enterococcus faecalis. Studies on the distribution of the gene encoding this novel surface protein, Esp, reveal a significant (P < 0.001) enrichment in infection-derived E. faecalis isolates. Interestingly, the esp gene was not identified in any of 34 clinical E. faecium isolates or in 4 other less pathogenic enterococcal species tested. Analysis of the structural gene among various E. faecalis isolates reveals the existence of alternate forms of expression of the Esp protein. The deduced primary structure of the Esp protein from strain MMH594, inferred to be 1,873 amino acids (aa) with a predicted mass of approximately 202 kDa, reveals a core region consisting of repeat units that make up 50% of the protein. Esp bears global organizational similarity to the Rib and C alpha proteins of group B streptococci. Identity among Esp, Rib, and C alpha proteins is strikingly localized to a stretch of 13 aa within repeats of similar length. The high degree of conservation of this 13-residue sequence suggests that it plays an important role in the natural selection for this trait among infection-derived E. faecalis and group B streptococcal isolates.
我们报告了粪肠球菌一种新的细胞壁相关蛋白的鉴定。对编码这种新型表面蛋白Esp的基因分布的研究表明，在感染源粪肠球菌分离株中该基因有显著（P < 0.001）富集。有趣的是，在34株临床屎肠球菌分离株或其他4种致病性较低的肠球菌检测菌株中均未鉴定到esp基因。对不同粪肠球菌分离株的结构基因分析揭示了Esp蛋白存在多种表达形式。从MMH594菌株推导的Esp蛋白一级结构，推测为1873个氨基酸（aa），预测分子量约为202 kDa，其核心区域由重复单元组成，占该蛋白的50%。Esp与B族链球菌的Rib和Cα蛋白在整体结构上相似。Esp、Rib和Cα蛋白之间的同源性显著集中在相似长度重复序列内的一段13个氨基酸区域。这13个残基序列的高度保守表明，它在感染源粪肠球菌和B族链球菌分离株的这一特性自然选择中发挥重要作用。
