Lee Philip A, Buchanan Grant, Stanley Nicola R, Berks Ben C, Palmer Tracy
Department of Molecular Microbiology, John Innes Centre, Norwich NR4 7UH, UK.
J Bacteriol. 2002 Nov;184(21):5871-9. doi: 10.1128/JB.184.21.5871-5879.2002.
The TatA and TatB proteins are essential components of the twin arginine protein translocation pathway in Escherichia coli. C-terminal truncation analysis of the TatA protein revealed that a plasmid-expressed TatA protein shortened by 40 amino acids is still fully competent to support protein translocation. Similar truncation analysis of TatB indicated that the final 30 residues of TatB are dispensable for function. Further deletion experiments with TatB indicated that removal of even 70 residues from its C terminus still allowed significant transport. These results imply that the transmembrane and amphipathic helical regions of TatA and TatB are critical for their function but that the C-terminal domains are not essential for Tat transport activity. A chimeric protein comprising the N-terminal region of TatA fused to the amphipathic and C-terminal domains of TatB supports a low level of Tat activity in a strain in which the wild-type copy of either tatA or tatB (but not both) is deleted.
TatA和TatB蛋白是大肠杆菌双精氨酸蛋白转运途径的重要组成部分。对TatA蛋白进行C端截短分析发现，截短40个氨基酸的质粒表达TatA蛋白仍完全能够支持蛋白转运。对TatB进行类似的截短分析表明，TatB的最后30个残基对于其功能是可有可无的。对TatB进行的进一步缺失实验表明，从其C端去除多达70个残基仍能实现显著的转运。这些结果表明，TatA和TatB的跨膜及两亲性螺旋区域对其功能至关重要，但C端结构域对于Tat转运活性并非必不可少。一种由TatA的N端区域与TatB的两亲性及C端结构域融合而成的嵌合蛋白，在tatA或tatB（但不是两者）的野生型拷贝被删除的菌株中支持低水平的Tat活性。
