Practice question

Tunnel guiding nascent polypeptide from catalytic site to exterior lies exclusively in large ribosomal subunit, 50S in bacteria, 60S in eukaryotes and 39S in mitochondria. Constructed from conserved rRNA domains, it is about 100 angstroms long and 10 to 20 angstroms wide, accommodating 30 to 40 amino acids in extended conformation. Its confinement restricts premature tertiary folding, promotes secondary structure formation, senses stalling sequences, and positions exit site where chaperones and translocation machinery interact, coupling synthesis to folding, localization and quality control essential for proteostasis.