Poulsen K, Reinholdt J, Kilian M
Institute of Medical Microbiology, Faculty of Health Sciences, University of Aarhus, Denmark.
J Bacteriol. 1992 May;174(9):2913-21. doi: 10.1128/jb.174.9.2913-2921.1992.
The bacterial immunoglobulin A1 (IgA1) proteases are putative virulence factors secreted by a number of human pathogens capable of penetrating the mucosal barrier. Among Haemophilus influenzae strains, the IgA1 protease is found in several allelic forms with different serological neutralizing properties. A comparison of the primary structures of four serologically distinct H. influenzae IgA1 proteases suggests that this variation is caused by epitopes of the discontinuous conformational type. Analysis of the homologies among the four iga genes indicates that the variation results from transformation and subsequent homologous recombination in the iga gene region among H. influenzae strains. We find evidence for gene rearrangements, including transpositions in the iga gene region encoding the secretory part of the IgA1 preprotease. The amino acid sequence of the C terminus of the preprotease (the beta-core), which is assumed to be involved in secretion of the protease by forming a pore in the outer membrane, is highly conserved. In contrast to conserved areas in the protease domain, the nucleotide sequence encoding the beta-core showed a striking paucity of synonymous site variation.
细菌免疫球蛋白A1（IgA1）蛋白酶是多种能够穿透黏膜屏障的人类病原体分泌的假定毒力因子。在流感嗜血杆菌菌株中，IgA1蛋白酶以几种具有不同血清学中和特性的等位基因形式存在。对四种血清学不同的流感嗜血杆菌IgA1蛋白酶一级结构的比较表明，这种变异是由不连续构象类型的表位引起的。对四个iga基因之间同源性的分析表明，这种变异是由流感嗜血杆菌菌株中iga基因区域的转化及随后的同源重组导致的。我们发现了基因重排的证据，包括在编码IgA1前蛋白酶分泌部分的iga基因区域中的转座。前蛋白酶C末端（β核心）的氨基酸序列被认为通过在外膜形成孔道参与蛋白酶的分泌，该序列高度保守。与蛋白酶结构域中的保守区域相反，编码β核心的核苷酸序列显示出同义位点变异极少。
