tailieunhanh - Báo cáo khoa học: 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 trans-port across the bacterial cytoplasmicmembrane 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 themembranemust 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). . | Eur. J. Biochem. 271 4779-4787 2004 FEBS 2004 doi Trigger factor interacts with the signal peptide of nascent Tat substrates but does not play a critical role in Tat-mediated export Wouter S. P. Jong1 Corinne M. ten Hagen-Jongman1 Pierre Genevaux2 Josef Brunner3 Bauke Oudega1 and Joen Luirink1 1 Department of Molecular Microbiology Institute of Molecular Cell Biology Vrije Universiteit Amsterdam the Netherlands 2 Department of Microbiology and Molecular Medicine Centre Medical Universitaire Geneva Switzerland 3 Institute of Biochemistry Eidgenossische Technische Hochschule Zurich Zurich Switzerland 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. Keywords Escherichia coli protein targeting signal peptide trigger factor twin-arginine translocation. In Escherichia coli most proteins that reside in the periplasmic space are synthesized as preproteins with a cleavable N-terminal signal peptide that mediates targeting to the inner membrane. Signal peptides classically have a tri-partite structure with a positively charged N-region a hydrophobic core and a polar C-region