Trigger factor binding to ribosomes with nascent peptide chains of varying lengths and sequences.
Trigger factor (TF) is the first protein-folding chaperone to interact with a nascent peptide chain as it emerges from the ribosome. Here, we have used a spin down assay to estimate the affinities for the binding of TF to ribosome nascent chain complexes (RNCs) with peptides of varying lengths and sequences. An in vitro system for protein synthesis assembled from purified Escherichia coli components was used to produce RNCs stalled on truncated mRNAs. The affinity of TF to RNCs exposing RNA polymerase sequences increased with the length of the nascent peptides. TF bound to RNA polymerase RNCs with significantly higher affinity than to inner membrane protein leader peptidase and bacterioopsin RNCs. The latter two RNCs are substrates for signal recognition particle, suggesting complementary affinities of TF and signal recognition particle to nascent peptides targeted for cytoplasm and membrane.
Raine
Amanda
A
Department of Pharmaceutical Biosciences, Box 591, Biomedical Centre, Uppsala University, 75124 Uppsala, Sweden.
Lovmar
Martin
M
Wikberg
Jarl
J
Ehrenberg
Måns
M
D000595:Amino Acid Sequence; D001436:Bacteriorhodopsins / Q000737:chemistry / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D019696:Peptidylprolyl Isomerase / Q000378:metabolism*; D012319:RNA Polymerase II / Q000737:chemistry / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism
D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D001436:Bacteriorhodopsins; C017827:bacterio-opsin; D012319:RNA Polymerase II; D012697:Serine Endopeptidases; C026515:type I signal peptidase; C403324:trigger factor, E coli; D019696:Peptidylprolyl Isomerase