Trigger factor interacts with the signal peptide of nascent Tat substrates but does not play a critical role in Tat-mediated export.
Twin-arginine translocation (Tat)-mediated protein transport across the bacterial cytoplasmic membrane occurs only after synthesis and folding of the substrate protein that contains a signal peptide with a characteristic twin-arginine motif. This implies that premature contact between the Tat signal peptide and the Tat translocon in the membrane must be prevented. We used site-specific photo-crosslinking to demonstrate that the signal peptide of nascent Tat proteins is in close proximity to the chaperone and peptidyl-prolyl isomerase trigger factor (TF). The contact with TF was strictly dependent on the context of the translating ribosome, started early in biogenesis when the nascent chain left the ribosome near L23, and persisted until the chain reached its full length. Despite this exclusive and prolonged contact, depletion or overexpression of TF had little effect on the kinetics and efficiency of the Tat export process.
Jong
Wouter S P
WS
Department of Molecular Microbiology, Institute of Molecular Cell Biology, Vrije Universiteit, Amsterdam, The Netherlands.
ten Hagen-Jongman
Corinne M
CM
Genevaux
Pierre
P
Brunner
Josef
J
Oudega
Bauke
B
Luirink
Joen
J
D001483:Base Sequence; D017931:DNA Primers; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D019696:Peptidylprolyl Isomerase / Q000378:metabolism*; D010957:Plasmids; D011485:Protein Binding; D014176:Protein Biosynthesis; D021382:Protein Sorting Signals; D013379:Substrate Specificity
D017931:DNA Primers; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; C408585:twin-arginine translocase complex, E coli; C403324:trigger factor, E coli; D019696:Peptidylprolyl Isomerase