Wang Ying
University of Southern California School of Dentistry, 925 W. 34th Street, Los Angeles, California 9008, USA.
Biochem Biophys Res Commun. 2002 Mar 29;292(2):396-401. doi: 10.1006/bbrc.2002.6657.
Outer membrane protein A (OmpA) is a major protein in the Escherichia coli outer membrane. In this study, the function of OmpA in E. coli stress survival was examined. An E. coli K1 ompA-deletion mutant was significantly more sensitive than that of its parent strain to sodium dodecyl sulfate (SDS), cholate, acidic environment, high osmolarity, and pooled human serum. A number of amino acid changes at the extracellular loops of OmpA did not affect the viability of E. coli, while short peptide insertions in the periplasmic turns of the OmpA beta-barrel decreased E. coli resistance to environmental stresses. Moreover, ompA mutants were found to survive much better within brain microvascular endothelial cells than the wild-type strain, supporting that OmpA is a major target in mammalian host cell defense. These results indicated that OmpA plays a vital structural role in E. coli, and suggested that a perfect beta-barrel structure of OmpA is important for outer membrane stability. Based on these results and the published OmpA structural analyses, I propose that OmpA is composed of three functional domains including a hydrophilic extracellular mass, a beta-barrel transmembrane structure, and a peptidoglycan binding domain.
外膜蛋白A（OmpA）是大肠杆菌外膜中的一种主要蛋白质。在本研究中，检测了OmpA在大肠杆菌应激存活中的功能。一株大肠杆菌K1 ompA缺失突变体对十二烷基硫酸钠（SDS）、胆酸盐、酸性环境、高渗透压和人混合血清的敏感性明显高于其亲本菌株。OmpA细胞外环上的一些氨基酸变化不影响大肠杆菌的生存能力，而在OmpAβ桶周质转角处插入短肽会降低大肠杆菌对环境应激的抗性。此外，发现ompA突变体在脑微血管内皮细胞内存活情况比野生型菌株好得多，这支持了OmpA是哺乳动物宿主细胞防御中的主要靶点。这些结果表明，OmpA在大肠杆菌中起着至关重要的结构作用，并表明OmpA完美的β桶结构对外膜稳定性很重要。基于这些结果和已发表的OmpA结构分析，我提出OmpA由三个功能域组成，包括一个亲水性细胞外物质、一个β桶跨膜结构和一个肽聚糖结合域。
