SecA, an essential component of the secretory machinery of Escherichia coli, exists as homodimer.
Size exclusion chromatography of the cytosolic fraction of SecA-overproducing cells of Escherichia coli suggested that SecA, an essential component of the secretory machinery, exists as an oligomer. The subunit structure of SecA was then studied using a purified specimen. Estimation of the molecular mass by means of ultracentrifugation and chemical crosslinking analysis revealed that SecA exists as a homodimer. The purified SecA was denatured in 6 M guanidine-HCl and renatured to a dimer, which was fully active in terms of translocation, even in the presence of 1 mM dithiothreitol. It is suggested that the dimeric structure is not critically maintained by disulfide bonding between the two subunits, each of which contains four cysteine residues.
Akita
M
M
Institute of Applied Microbiology, University of Tokyo, Japan.
Shinkai
A
A
Matsuyama
S
S
Mizushima
S
S
D000251:Adenosine Triphosphatases / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D001692:Biological Transport; D003432:Cross-Linking Reagents / Q000737:chemistry*; D003600:Cytosol / Q000737:chemistry / Q000187:drug effects; D004220:Disulfides; D004229:Dithiothreitol / Q000494:pharmacology; D004926:Escherichia coli / Q000737:chemistry* / Q000187:drug effects; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D011489:Protein Denaturation; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D014461:Ultracentrifugation
D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; D004220:Disulfides; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins; D004229:Dithiothreitol