The ribosome, one of the largest molecular machines in living cells, is in charge of protein synthesis. Ribosomes are the birth place of proteins in living cells. It is an RNA-protein complex. The ribosomal small subunit is mainly responsible for decoding the genetic information carried on messenger RNA (mRNA) while the large subunit elongates the nascent protein chain by catalyzing the formation of peptide bonds. During the synthesis the nascent chain migrates through a tunnel in the large subunit, the so-called exit tunnel, to exit the ribosome. For a long time the exit tunnel was considered to be a passive conduction channel for the nascent protein to migrate through, however, an increasing number of studies have shown that the exit tunnel is actually involved in many co-translational activities of the nascent peptides, such as folding of the nascent chain inside the exit tunnel, translation stalling of certain peptide and antibiotic binding and resistance. Detailed insights into the architecture of the tunnel have been obtained from X-ray and cryo-EM structures of prokaryotic and eukaryotic ribosomes. Protein biogenesis factors are thought to bind to NC not before they exit the ribosomal exit tunnel, one such factor involvement with NC is the Nascent Chain Association Complex. This review provides an insight and understanding about the functionality of the Ribosome tunnel and its association with the nascent peptide chain.

Keywords: Ribosome, Ribosome Exit Tunnel, NAC complex, Nascent polypeptide chain.