Band 1 subunit of Escherichia coli preportein 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 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.
Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755-3844.
K
K
Douville
M
M
Leonard
L
L
Brundage
K
K
Nishiyama
H
H
Tokuda
S
S
Mizushima
W
W
Wickner
D000251:Adenosine Triphosphatases / Q000737:chemistry*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001692:Biological Transport; D015153:Blotting, Western; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism*; D029968:Escherichia coli Proteins; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D010455:Peptides / Q000276:immunology; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010455:Peptides; D000069816:SEC Translocation Channels; C065493:SecE protein, E coli; C057841:SecY protein, E coli; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins