The TatBC Complex of the Tat Protein Translocase in Escherichia coli and Its Transition to the Substrate-Bound TatABC Complex
The TatBC Complex of the Tat Protein Translocase in Escherichia coli and Its Transition to the Substrate-Bound TatABC Complex
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DOI：
10.1021/bi500169s
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发表时间：
2014-04-15
期刊：
影响因子：
2.9
通讯作者：
Brueser, Thomas
中科院分区：
文献类型：
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作者：
Behrendt, Jana;Brueser, Thomas
双精氨酸转位(TAT)系统用于跨原核生物和植物质体的膜运输折叠蛋白。在大肠杆菌中，由多个拷贝的TatB和TatC组成的复合体通过结合TAT底物上的信号肽来启动转运。利用蓝色天然聚丙烯酰胺凝胶电泳法，可在440和580 kDa的分子质量处检测到含TatBC的络合物的条带。我们系统地分析了Tat与TatB或TatC变异体形成的复合体，这些变异体在选定的位置携带点突变。几个突变导致了特定的拆解模式和440 kDa：580 kDa复合体比率的变化。440 kDa复合体只含有TatBC，而580 kDa复合体由TatABC组成。底物结合在500 kDa附近形成TatBC-TAT底物复合体，在600 kDa附近形成TatABC-Tat底物复合体。只有与600 kDa相似的复合体在非重组底物水平上被检测到，因此可能是生理上最相关的物种。结果表明，一些TATA通常与TatBC有关，与底物结合无关。
The twin-arginine translocation (Tat) system serves to transport folded proteins across membranes of prokaryotes and plant plastids. In Escherichia coli, a complex consisting of multiple copies of TatB and TatC initiates the transport by binding the signal peptides of the Tat substrates. Using blue-native polyacrylamide gel electrophoresis, bands of TatBC-containing complexes can be detected at molecular masses of 440 and 580 kDa. We systematically analyzed the formation of Tat complexes with TatB or TatC variants that carried point mutations at selected positions. Several mutations resulted in specific disassembly patterns and alterations in the 440 kDa:580 kDa complex ratios. The 440 kDa complex contains only TatBC, whereas the 580 kDa complex consists of TatABC. Substrate binding results in a TatBC-Tat substrate complex at similar to 500 kDa and a TatABC-Tat substrate complex at similar to 600 kDa. Only the similar to 600 kDa complex was detected with nonrecombinant substrate levels and thus could be the physiologically most relevant species. The results suggest that some TatA is usually associated with TatBC, regardless of substrate binding.