Jc. Joly et al., SUBUNIT DYNAMICS IN ESCHERICHIA-COLI PREPROTEIN TRANSLOCASE, Proceedings of the National Academy of Sciences of the United Statesof America, 91(11), 1994, pp. 4703-4707
SecY, SecE, and band 1 copurify as the SecY/E integral membrane domain
of Escherichia coli preprotein translocase. To measure the in vivo as
sociation of these polypeptides and assay possible exchange, plasmid-b
orne secY and secE genes were placed under control of the ara regulon
and fused to DNA encoding the influenza hemagglutinin epitope. Cells w
ere incubated with [S-35]methionine, grown for a ''chase'' period, and
then induced with arabinose to express epitope-tagged, nonradioactive
SecY and SecE. Both the wild-type and epitope-tagged polypeptides ass
embled into functional, heterotrimeric SecY/E complex. However, immuno
precipitation with antibody to the epitope tag did not cross-precipita
te radiolabeled SecY or SecE. Thus, these subunits normally associate
stably in vivo.