PMID:9351821

Citation	Matsumoto, G, Yoshihisa, T and Ito, K (1997) SecY and SecA interact to allow SecA insertion and protein translocation across the Escherichia coli plasma membrane. EMBO J. 16:6384-93
Abstract	SecA, the preprotein-driving ATPase in Escherichia coli, was shown previously to insert deeply into the plasma membrane in the presence of ATP and a preprotein; this movement of SecA was proposed to be mechanistically coupled with preprotein translocation. We now address the role played by SecY, the central subunit of the membrane-embedded heterotrimeric complex, in the SecA insertion reaction. We identified a secY mutation (secY205), affecting the most carboxyterminal cytoplasmic domain, that did not allow ATP and preprotein-dependent productive SecA insertion, while allowing idling insertion without the preprotein. Thus, the secY205 mutation might affect the SecYEG 'channel' structure in accepting the preprotein-SecA complex or its opening by the complex. We isolated secA mutations that allele-specifically suppressed the secY205 translocation defect in vivo. One mutant protein, SecA36, with an amino acid alteration near the high-affinity ATP-binding site, was purified and suppressed the in vitro translocation defect of the inverted membrane vesicles carrying the SecY205 protein. The SecA36 protein could also insert into the mutant membrane vesicles in vitro. These results provide genetic evidence that SecA and SecY specifically interact, and show that SecY plays an essential role in insertion of SecA in response to a preprotein and ATP and suggest that SecA drives protein translocation by inserting into the membrane in vivo.
Links	PubMed PMC1170245 Online version:10.1093/emboj/16.21.6384
Keywords	Adenosine Triphosphatases/genetics; Adenosine Triphosphatases/metabolism; Alleles; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Biological Transport, Active; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli Proteins; Macromolecular Substances; Membrane Proteins/genetics; Membrane Proteins/metabolism; Membrane Transport Proteins; Mutagenesis; Phenotype; Point Mutation; Protein Precursors/metabolism; Suppression, Genetic; Transduction, Genetic
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