Band 1 subunit of Escherichia coli preprotein translocase and integral membrane export factor P12 are the same protein

Escherichia coli preprotein translocase consists of the peripheral membrane protein SecA and the integral membrane domain SecY/E. SecY/E, whether isolated chromatographically or by immunoprecipitation, was found to be a complex of three polypeptides, SecY, SecE, and band 1. Band 1 did not correspond...

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Bibliographic Details
Published in:The Journal of biological chemistry 1994-07, Vol.269 (29), p.18705-18707
Main Authors: DOUVILLE, K, LEONARD, M, BRUNDAGE, L, NISHIYAMA, K.-I, TOKUDA, H, MIZUSHIMA, S, WICKNER, W
Format: Article
Language:English
Subjects:
Biological and medical sciences
Cell physiology
Escherichia coli
Fundamental and applied biological sciences. Psychology
Molecular and cellular biology
Secretion. Exocytosis
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Summary:Escherichia coli preprotein translocase consists of the peripheral membrane protein SecA and the integral membrane domain SecY/E. SecY/E, whether isolated chromatographically or by immunoprecipitation, was found to be a complex of three polypeptides, SecY, SecE, and band 1. Band 1 did not correspond to a known sec gene product. The independent purification of the separate integral membrane polypeptides needed for reconstitution of translocation yielded SecY, SecE, and a protein that we termed P12. Based on the sequence of P12, we have prepared antisera to a carboxyl-terminal peptide domain and shown that this antiserum specifically labels only P12 on immunoblots of inner membrane vesicles. We now report that affinity-purified anti-P12 antibodies specifically label the band 1 subunit of the SecY/E complex, whether the SecY/E was isolated chromatographically or by precipitation with antibodies to an epitope-tagged SecY subunit. In addition, the antiserum to P12 can specifically immunoprecipitate the full three-subunit SecY/E complex from detergent extracts. This finding completes the identification of the polypeptides that are essential for catalysis of preprotein translocation.
ISSN:0021-9258
1083-351X