Interplay of signal recognition particle and trigger factor at L23 near the nascent chain exit site on the Escherichia coli ribosome.
As newly synthesized polypeptides emerge from the ribosome, they interact with chaperones and targeting factors that assist in folding and targeting to the proper location in the cell. In Escherichia coli, the chaperone trigger factor (TF) binds to nascent polypeptides early in biosynthesis facilitated by its affinity for the ribosomal proteins L23 and L29 that are situated around the nascent chain exit site on the ribosome. The targeting factor signal recognition particle (SRP) interacts specifically with the signal anchor (SA) sequence in nascent inner membrane proteins (IMPs). Here, we have used photocross-linking to map interactions of the SA sequence in a short, in vitro-synthesized, nascent IMP. Both TF and SRP were found to interact with the SA with partially overlapping binding specificity. In addition, extensive contacts with L23 and L29 were detected. Both purified TF and SRP could be cross-linked to L23 on nontranslating ribosomes with a competitive advantage for SRP. The results suggest a role for L23 in the targeting of IMPs as an attachment site for TF and SRP that is close to the emerging nascent chain.
Ullers
Ronald S
RS
Department of Molecular Microbiology, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands.
Houben
Edith N G
EN
Raine
Amanda
A
ten Hagen-Jongman
Corinne M
CM
Ehrenberg
Måns
M
Brunner
Joseph
J
Oudega
Bauke
B
Harms
Nellie
N
Luirink
Joen
J
D001426:Bacterial Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000166:cytology / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D019696:Peptidylprolyl Isomerase / Q000378:metabolism*; D011485:Protein Binding; D014176:Protein Biosynthesis; D012269:Ribosomal Proteins / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D018271:Signal Recognition Particle / Q000378:metabolism*
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C082931:Ffh protein, E coli; C068023:FtsQ protein, E coli; D008565:Membrane Proteins; D012269:Ribosomal Proteins; D018271:Signal Recognition Particle; C043816:ribosomal protein L23, E coli; C035078:ribosomal protein L29; C403324:trigger factor, E coli; D019696:Peptidylprolyl Isomerase