SecA Suppresses the Temperature-Sensitive SecY24 Defect in Protein Translocation in Escherichia coli Membrane Vesicles

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 85; no. 23; pp. 8953 - 8957
• Main Authors: Fandl, James P., Cabelli, Robert, Oliver, Donald, Tai, Phang C.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01-12-1988; National Acad Sciences
• Subjects: Bacterial Proteins - genetics; Biochemistry; Biological and medical sciences; Cell Membrane - metabolism; Cell membranes; Cell membranes. Ionic channels. Membrane pores; Cell structures and functions; Centrifugation; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Fundamental and applied biological sciences. Psychology; Genes, Bacterial; Genetic mutation; Kinetics; Medical genetics; Membrane Proteins - genetics; Messenger RNA; Molecular and cellular biology; Molecular genetics; Mutation; P branes; Plasmids; Protein precursors; Protein Processing, Post-Translational; Protein transport; Suppression, Genetic; Temperature
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.85.23.8953

Genetic analysis of protein secretion in Escherichia coli has identified secY/prlA and secA as components of the secretory apparatus. We have examined the roles of the secY(prlA) gene product (an integral membrane protein) and the soluble secA gene product in translocation of OmpA and alkaline phosphatase precursors in an in vitro system. The protein translocation defect of the secY24 mutation was recently demonstrated in vitro as was its suppression by an S300 extract. We show here that the extract was essentially inactive in SecY24 suppression when SecA protein was removed from it by immunoaffinity chromatography. Furthermore, purified SecA protein suppressed the SecY24 defect. Preincubation of the inactivated SecY24 membrane vesicles either with S300 containing SecA or with purified SecA protein reconstituted the membranes and restored the translocation activity when assayed in the absence of additional soluble proteins. These results suggest that the SecY24 translocation defect is suppressed by SecA interacting, directly or indirectly, with SecY24 on the cytoplasmic membrane.