Cotranslational protein folding within the ribosome tunnel influences trigger-factor recruitment.
In recent years, various folding zones within the ribosome tunnel have been identified and explored through x-ray, cryo-electron microscopy (cryo-EM), and molecular biology studies. Here, we generated ribosome-bound nascent polypeptide complexes (RNCs) with different polyalanine (poly-A) inserts or signal peptides from membrane/secretory proteins to explore the influence of nascent chain compaction in the Escherichia coli ribosome tunnel on chaperone recruitment. By employing time-resolved fluorescence resonance energy transfer and immunoblotting, we were able to show that the poly-A inserts embedded in the passage tunnel can form a compacted structure (presumably helix) and reduce the recruitment of Trigger Factor (TF) when the helical motif is located in the region near the tunnel exit. Similar experiments on nascent chains containing signal sequences that may form compacted structural motifs within the ribosome tunnel and lure the signal recognition particle (SRP) to the ribosome, provided additional evidence that short, compacted nascent chains interfere with TF binding. These findings shed light on the possible controlling mechanism of nascent chains within the tunnel that leads to chaperone recruitment, as well as the function of L23, the ribosomal protein that serves as docking sites for both TF and SRP, in cotranslational protein targeting.
Institute of Chemistry, Academia Sinica, Nankang, Taipei, Taiwan.
Ku-Feng
KF
Lin
Chia-Sui
CS
Sun
Yi-Chen
YC
Huang
Sunney I
SI
Chan
Jiri
J
Koubek
Tzong-Huah
TH
Wu
Joseph J-T
JJ
Huang
D000595:Amino Acid Sequence; D029968:Escherichia coli Proteins / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D008565:Membrane Proteins / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism*; D019696:Peptidylprolyl Isomerase / Q000378:metabolism*; D011061:Poly A / Q000378:metabolism; D014176:Protein Biosynthesis; D017510:Protein Folding; D021382:Protein Sorting Signals; D017433:Protein Structure, Secondary; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D018271:Signal Recognition Particle / Q000378:metabolism
D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D021382:Protein Sorting Signals; D018271:Signal Recognition Particle; D011061:Poly A; D012343:RNA, Transfer; C403324:trigger factor, E coli; D019696:Peptidylprolyl Isomerase