Properties of intraribosomal part of nascent polypeptide

This review analyzes the concept according to which the pathway of synthesized peptide from the ribosome peptidyl transferase center to the exit domain goes along the tunnel of the large subparticle. Experimental data on the accessibility of the nascent polypeptide chain to molecules of modifying agents and fluorescence quenchers are considered. Results of localization of the exit site for the nascent peptide on the ribosome surface, possible conformational states of the peptide, and its mobility and folding on the ribosome are analyzed. The analysis is based on the ribosomal tunnel parameters obtained using X-ray crystallography of whole ribosomes and large ribosomal subparticles. Special attention is given to data that do not fit in the concept of the “tunnel for peptide exit“ and to results already obtained before the reliable tunnel visualization using X-ray crystallography was achieved.