Bioinformatic analyses of Gram-negative bacterial OstA outer membrane assembly homologues
Bioinformatic analyses of Gram-negative bacterial OstA outer membrane assembly homologues
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DOI：
10.2174/138920206779116765
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发表时间：
2006-11-01
期刊：
影响因子：
2.6
通讯作者：
Saier, Milton H., Jr.
中科院分区：
文献类型：
--
作者：
Hu, Kuang-Yu;Saier, Milton H., Jr.
OstA（Imp）同源物已被证明在外膜生物发生中发挥作用。生物信息学分析这些蛋白质的生物体与完全测序的基因组显示，这些蛋白质只发生在细菌与两个膜。鉴定了两种OstA类型，大OstA（L; 812 +/- 94个残基）和小OstA（S; 181 +/- 25个残基）。S仅具有OstA结构域，而L具有该结构域加上更大的非同源OstA-C结构域。缺乏S和L蛋白的细菌主要限于基因组大小减小的病原体和共生体。这些细菌中的几种似乎也具有典型革兰氏阴性细菌脂多糖（LPS）的生物合成所需的不完整基因组。S和L同源物的系统发育分析表明，它们通常遵循来自相同生物体的16 S rRNA的同源性，只有少数例外。它们可能包含两组蛋白质的正向排列，共同促进单一的统一功能。虽然大多数生物都有一个L和一个S，但那些缺乏S但拥有L的生物比那些缺乏L但拥有S的生物要多。根据我们的研究结果和其他人的研究结果，我们认为：（1）L和S蛋白对于外膜组装是不必要的，（2）它们通常在大分子插入中一起起作用，（3）它们对于外膜的外叶中适当的LPS组装是重要的，（4）它们特异性地起将LPS输出到外叶的作用，以及（5）L提供主要功能，而S提供重要的辅助功能。
OstA (Imp) homologues have been shown to play a role in outer membrane biogenesis. Bioinformatic analyses of these proteins in organisms with fully sequenced genomes reveal that these proteins occur only in bacteria with two membranes. Two OstA types were identified, large OstAs (L; 812 +/- 94 residues) and small OstAs (S; 181 +/- 25 residues). S possesses only the OstA domain while L has this domain plus a larger nonhomologous OstA-C domain. Bacteria lacking both S and L proteins were primarily restricted to reduced genome size pathogens and symbionts. Several of these bacteria appear to also have incomplete sets of genes required for the biosynthesis of typical Gram-negative bacterial lipopolysaccharide (LPS). Phylogenetic analyses of both S and L homologues showed that they generally follow the phylogenies of the 16S rRNAs from the same organisms with few exceptions. They may comprise two orthologous sets of proteins that together facilitate a single unified function. While most organisms possess a single L and a single S, those lacking S but possessing L are more numerous than those lacking L but possessing S. Based on our findings and those of others, we suggest that (1) the L and S proteins are nonessential for outer membrane assembly, (2) they normally act together in macromolecular insertion, (3) they are important for proper LPS assembly in the outer leaflet of the outer membrane, (4) they function specifically to export LPS to the outer leaflet, and (5) L provides a primary function while S provides an important auxiliary function.