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首页> 外文期刊>Journal of bacteriology >Characterization of Streptococcus gordonii SecA2 as a Paralogue of SecA
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Characterization of Streptococcus gordonii SecA2 as a Paralogue of SecA

机译：戈登链球菌SecA2作为SecA旁系的表征。

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The accessory Sec system of Streptococcus gordonii is essential for transport of the glycoprotein GspB to the bacterial cell surface. A key component of this dedicated transport system is SecA2. The SecA2 proteins of streptococci and staphylococci are paralogues of SecA and are presumed to have an analogous role in protein transport, but they may be specifically adapted for the transport of large, serine-rich glycoproteins. We used a combination of genetic and biochemical methods to assess whether the S. gordonii SecA2 functions similarly to SecA. Although mutational analyses demonstrated that conserved amino acids are essential for the function of SecA2, replacing such residues in one of two nucleotide binding folds had only minor effects on SecA2 function. SecA2-mediated transport is highly sensitive to azide, as is SecA-mediated transport. Comparison of the S. gordonii SecA and SecA2 proteins in vitro revealed that SecA2 can hydrolyze ATP at a rate similar to that of SecA and is comparably sensitive to azide but that the biochemical properties of these enzymes are subtly different. That is, SecA2 has a lower solubility in aqueous solutions and requires higher Mg2+ concentrations for maximal activity. In spite of the high degree of similarity between the S. gordonii paralogues, analysis of SecA-SecA2 chimeras indicates that the domains are not readily interchangeable. This suggests that specific, unique contacts between SecA2 and other components of the accessory Sec system may preclude cross-functioning with the canonical Sec system.
机译：戈登链球菌的辅助Sec系统对于糖蛋白GspB向细菌细胞表面的运输至关重要。该专用运输系统的关键组件是SecA2。链球菌和葡萄球菌的SecA2蛋白是SecA的旁系同源物，推测在蛋白质转运中具有类似的作用，但它们可能特别适合于转运富含丝氨酸的大糖蛋白。我们使用了遗传和生化方法的组合来评估 S。 gordonii SecA2的功能类似于SecA。尽管突变分析表明保守的氨基酸对于SecA2的功能至关重要，但是在两个核苷酸结合折叠之一中替换此类残基对SecA2的功能影响很小。 SecA2介导的转运对叠氮化物高度敏感，SecA介导的转运也是如此。 S的比较。戈登氏SecA和SecA2蛋白在体外显示，SecA2可以以类似于SecA的速率水解ATP，并且对叠氮化物比较敏感，但是这些酶的生化特性略有不同。也就是说，SecA2在水溶液中的溶解度较低，并且需要更高的Mg 2 + 浓度才能发挥最大活性。尽管 S之间具有高度相似性。 gordonii 旁系同源物，对SecA-SecA2嵌合体的分析表明，这些域不容易互换。这表明，SecA2与附件Sec系统的其他组件之间的特定，唯一接触可能会阻止规范Sec系统的交叉功能。

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