Gophna Uri, Ideses Diana, Rosen Ran, Grundland Adam, Ron Eliora Z
Department of Molecular Microbiology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
Int J Med Microbiol. 2004 Oct;294(6):373-81. doi: 10.1016/j.ijmm.2004.08.004.
OmpA is an important constituent of the outer membrane of Gram-negative bacteria. OmpA is involved in a variety of host-bacteria interactions, including crossing of the blood-brain barrier by E. coli strains causing newborn meningitis, and elicits a significant response by the immune system of the host. The bactericidal effect of neutrophil elastase (NE) is also attributed to degradation of the bacterial OmpA. Here we examined the OmpA of septicemic E. coli 078 strains and show that two surface-exposed loops are conserved among invasive strains of E. coli and other pathogenic Enterobacteriaceae. In addition, there is evidence for convergent evolution, implying the existence of selective pressure. Our results also indicate that large quantities of OmpA are secreted into the medium during all phases of growth, where it is present both in secreted vesicles and as a soluble secreted protein. We assume that secreted OmpA can play a role in protection of bacteria from NE by competitive inhibition. Support for this assumption was obtained from experiments indicating that addition of exogenous, purified OmpA reduces killing of bacteria by NE.
外膜蛋白A（OmpA）是革兰氏阴性菌外膜的重要组成部分。OmpA参与多种宿主-细菌相互作用，包括导致新生儿脑膜炎的大肠杆菌菌株穿越血脑屏障，并引发宿主免疫系统的显著反应。中性粒细胞弹性蛋白酶（NE）的杀菌作用也归因于对细菌OmpA的降解。在此，我们检测了败血症大肠杆菌078菌株的OmpA，并表明在大肠杆菌的侵袭性菌株和其他致病性肠杆菌科细菌中，有两个表面暴露环是保守的。此外，有趋同进化的证据，这意味着存在选择压力。我们的结果还表明，在生长的各个阶段，大量的OmpA被分泌到培养基中，它既存在于分泌小泡中，也作为可溶性分泌蛋白存在。我们假设分泌的OmpA可以通过竞争性抑制在保护细菌免受NE作用方面发挥作用。从实验中获得了对这一假设的支持，这些实验表明添加外源性纯化的OmpA可减少NE对细菌的杀伤。
