Bacterial 50S ribosomal subunit nascent peptide exit tunnel (NPET)

The bacterial 50S ribosomal subunit nascent peptide exit tunnel (NPET) is a structural channel that extends from the peptidyl transferase center (PTC) to the exterior of the large ribosomal subunit. Its primary biological function is to provide a protected path for the newly synthesized polypeptide chain to emerge from the ribosome during translation. The tunnel is not a passive conduit; its walls, composed mainly of 23S ribosomal RNA and specific ribosomal proteins like L4 and L22, interact with the nascent peptide to regulate translation speed and folding. In the context of infectious disease, the NPET is a major pharmacological target for several classes of antibiotics, including macrolides, lincosamides, and streptogramins. These drugs bind to specific sites within the tunnel, physically obstructing the exit of the peptide chain and causing the ribosome to stall. This inhibition of protein synthesis is bacteriostatic or bactericidal, making the NPET one of the most clinically significant targets in the treatment of Gram-positive and Gram-negative bacterial infections.

Other names

Ribosomal exit tunnel50S exit tunnelPolypeptide exit tunnelRibosomal tunnel

Inhibition of bacterial protein synthesis by sterically blocking the passage of the nascent polypeptide chain through the exit tunnel, leading to premature dissociation of peptidyl-tRNA from the ribosome.