期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 374, 期 2, 页码 283-291出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2007.09.050
关键词
twin-arginine translocase; TatC; signal peptide recognition; flow cytometry; suppressors
资金
- NIGMS NIH HHS [1 R01 GM069872, R01 GM069872, R01 GM069872-01A1] Funding Source: Medline
In vitro studies have suggested that the TatBC complex serves as the receptor for signal peptides targeted for export via the twin-arginine translocation (Tat) pathway. Substitution of the hallmark twin-arginine dipeptide with two lysines abrogates export of physiological substrates in all organisms. We report the isolation and characterization of suppressor mutations that allow export of an ssTor(KK)-GFP-SsrA tripartite fusion. We identified two amino acid suppressor mutations in the first cytoplasmic loop of TatC. In addition, two other an-Lino acids in the first cytoplasmic loop exhibit epistatic suppression. Surprisingly, we also identified a suppressor mutation predicted to lie within the second periplasmic loop of TatC, a region that is not expected to interact directly with the signal peptide. The suppressor mutations allowed export of the native Esherichia coli Tat substrate trimethylamine N-oxide reductase with a twin-lysine substitution in its signal sequence. The cytoplasmic suppressor mutations conferred SDS sensitivity and partial filamentation, indicating that Tat export of authentic substrates was impaired. (c) 2007 Elsevier Ltd. All rights reserved.
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