细菌蛋白质Tat转运系统的研究进展

Progress on the Bacterial Tat Protein Translocation System

蛋白质Tat转运系统不同于细菌中普遍存在的Sec转运系统 ,而与植物叶绿体中蛋白质转运的ΔpH依赖系统相似 .通过Tat系统转运的蛋白质底物含有特征性的双精氨酸保守序列核心S/T R R x F L K的信号肽 ,其h区的疏水性低 ,c区有由高赖氨酸、高精氨酸构成的避开Sec系统信号 ,信号肽和成熟蛋白质的组成对蛋白质的转运都有影响 .TatA、TatB、TatC和TatE四种蛋白质参与了大肠杆菌的Tat转运系统 .被转运的底物蛋白质绝大多数为与细菌厌氧呼吸有关的含氧化还原辅因子的酶 ,并以折叠形式转运 .

The bacterial Tat protein translocation system is different with the Sec machinery which is general protein translocation system in the bacteria, but similar to Delta pH-dependent pathway used for importing chloroplast proteins into the thylakoid. This system can export proteins with a twin-arginine signal peptide bearing a consensus (S/T) -R-R-x-F-L-K motif and in the folded conformation. Moreover most of these proteins are always containing redox cofactor enzymes with relations to the bacterial anaerobic respiratory. This protein translocation system is affected by a kind of factors such as the twin arginines in the consensus motif, the hydrophobicity of h-region, sec-avoidance signal of the c-region of the signal peptide and the constitution of mature proteins. And there are four proteins (TatA, TatB, TatC and TatE) involved with this system of E. coli.