An accessory sec locus of Streptococcus gordonii is required for export of the surface protein GspB and for normal levels of binding to human platelets
An accessory sec locus of Streptococcus gordonii is required for export of the surface protein GspB and for normal levels of binding to human platelets
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DOI：
10.1046/j.1365-2958.2002.02949.x
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发表时间：
2002-05-01
影响因子：
3.6
通讯作者：
Sullam, PM
中科院分区：
文献类型：
--
作者：
Bensing, BA;Sullam, PM
蛋白质跨细菌细胞膜的转运是由Sec系统的高度保守组分进行的。大多数细菌物种具有编码SecA和SecY的基因的单拷贝，这对生存力至关重要。然而，戈登链球菌菌株M99编码SecA和SecY同源物，其对于大多数输出蛋白的活力或易位不是必需的。基因（secA 2和secY 2）位于输出GspB（286 kDa细胞壁锚定蛋白）所需的染色体区域中。GspB表面表达的丧失与M99与人血小板结合的显著减少相关，表明其可能是粘附素。遗传分析表明，M99有第二个典型的SecA同源物，这是生存所必需的。至少有两个其他革兰氏阳性菌，肺炎链球菌和金黄色葡萄球菌，编码两套SecA和SecY同源物。一组与大肠杆菌的SecA和SecY更相似，而另一组与菌株M99的SecA 2和SecY 2更相似。SecY 2-SecA 2基因座中基因的保守组织表明，在这些革兰氏阳性物种中的每一个中，SecA 2和SecY 2可以构成用于转运非常大的富含丝氨酸的重复蛋白的专门系统。
The translocation of proteins across the bacterial cell membrane is carried out by highly conserved components of the Sec system. Most bacterial species have a single copy of the genes encoding SecA and SecY, which are essential for viability. However, Streptococcus gordonii strain M99 encodes SecA and SecY homologues that are not required for viability or for the translocation of most exported proteins. The genes (secA2 and secY2 ) reside in a region of the chromosome required for the export of GspB, a 286 kDa cell wall-anchored protein. Loss of GspB surface expression is associated with a significant reduction in the binding of M99 to human platelets, suggesting that it may be an adhesin. Genetic analyses indicate that M99 has a second, canonical SecA homologue that is essential for viability. At least two other Gram-positive species, Streptococcus pneumoniae and Staphylococcus aureus , encode two sets of SecA and SecY homologues. One set is more similar to SecA and SecY of Escherichia coli , whereas the other set is more similar to SecA2 and SecY2 of strain M99. The conserved organization of genes in the secY2-secA2 loci suggests that, in each of these Gram-positive species, SecA2 and SecY2 may constitute a specialized system for the transport of a very large serine-rich repeat protein.