Subunit interactions in the Escherichia coli protein translocase: SecE and SecG associate independently with SecY
Subunit interactions in the Escherichia coli protein translocase: SecE and SecG associate independently with SecY
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DOI：
10.1016/s0014-5793(97)00376-1
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发表时间：
1997-05-12
期刊：
影响因子：
3.5
通讯作者：
Ito, K
中科院分区：
文献类型：
--
作者：
Homma, T;Yoshihisa, T;Ito, K
我们使用六组氨酸标记的SecE和SecY来研究大肠杆菌蛋白转位酶的核心亚基(SecY、SecE和SecG)是如何相互作用的。从质膜中制备洗涤剂提取物，并用Ni2+-NTA琼脂糖亲和结合进行分级。虽然在野生型细胞中表达的His(6)-SecE同时下调了SecY和SecG的表达，但当同样的蛋白在secY24突变细胞中表达时，两者都没有被下调。不出所料，他的(6)-SecY同时拿下了Sece和SecG。有趣的是，他的(6)-SecY24能够拿下SecG，但不能拿下Sece。这些结果证实了我们先前的结论，即SecY24改变削弱了SecY-SecE的相互作用，并证明了SecY和SecG可以形成不含SecE的复合体。同样，可以从缺失secG的菌株中分离到SecY-SecE复合体。洗涤剂提取物中的三聚体复合体在23至26摄氏度的临界温度下解离，而不含SecG的SecY-SecE复合体在略低的温度(20-23摄氏度)下解离。我们的结论是，SecE和SecG各自独立地与蛋白质转位酶的中央亚单位SecY结合，尽管三聚体复合体比二聚体复合体更稳定。(C)1997年欧洲生化学会联合会。
We used hexahistidine-tagged SecE and SecY to study how the core subunits (SecY, SecE and SecG) of Escherichia coli protein translocase interact with each other. Detergent extracts were prepared from the plasma membranes and fractionated by Ni2+-NTA agarose affinity binding. Although His(6)-SecE, expressed in wild-type cells, brought down both SecY and SecG, neither of them was brought down when the same protein was expressed in the secY24 mutant cells. His(6)-SecY brought down both SecE and SecG, as expected. Interestingly, His(6)-SecY24 was able to bring down SecG but not SecE. These results confirm our previous conclusion that the secY24 alteration impairs the SecY-SecE interaction, and demonstrate that SecY and SecG can form a complex that does not contain SecE. Likewise, SecY-SecE complex could be isolated from the secG-deleted strain. The trimeric complex, in detergent extracts, dissociated at a critical temperature between 23 and 26 degrees C, whereas the SecY-SecE complex without SecG dissociated at a slightly lower temperature (20-23 degrees C). We conclude that each of SecE and SecG independently binds to SecY, the central subunit of protein translocase, although the trimeric complex is more stable than the binary complexes. (C) 1997 Federation of European Biochemical Societies.