Floyd Jeanetta Holley, You Zhipeng, Hsieh Ying-Hsin, Ma Yamin, Yang Hsuichin, Tai Phang C
Department of Biology, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, United States.
Department of Biology, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, United States.
Biochem Biophys Res Commun. 2014 Oct 10;453(1):138-42. doi: 10.1016/j.bbrc.2014.09.080. Epub 2014 Sep 27.
SecA is an essential multifunctional protein for the translocation of proteins across bacterial membranes. Though SecA is known to function in the membrane, the detailed mechanism for this process remains unclear. In this study we constructed a series of SecA N-terminal deletions and identified two specific domains crucial for initial SecA/membrane interactions. The first small helix, the linker and part of the second helix (Δ2-22) were found to be dispensable for SecA activity in complementing the growth of a SecA ts mutant. However, deletions of N-terminal aminoacyl residues 23-25 resulted in severe progressive retardation of growth. Moreover, a decrease of SecA activity caused by N-terminal deletions correlated to the loss of SecA membrane binding, formation of lipid-specific domains and channel activity. All together, the results indicate that the N-terminal aminoacyl residues 23-25 play a critical role for SecA binding to membranes and that the N-terminal limit of SecA for activity is at the 25th amino acid.
SecA是一种对于蛋白质跨细菌膜转运至关重要的多功能蛋白质。尽管已知SecA在膜中发挥作用，但该过程的详细机制仍不清楚。在本研究中，我们构建了一系列SecA N端缺失体，并鉴定出两个对于SecA与膜的初始相互作用至关重要的特定结构域。发现第一个小螺旋、连接区和第二个螺旋的一部分（Δ2-22）对于SecA在补充SecA温度敏感突变体生长方面的活性是可有可无的。然而，N端23-25位氨基酸残基的缺失导致生长严重且逐渐迟缓。此外，由N端缺失引起的SecA活性降低与SecA膜结合的丧失、脂质特异性结构域的形成以及通道活性相关。总之，结果表明N端23-25位氨基酸残基对于SecA与膜的结合起关键作用，并且SecA活性的N端界限位于第25个氨基酸处。
