ENZYMATIC-ACTIVITY OF THE RIBOSOME-BOUND NASCENT POLYPEPTIDE

Firefly luciferase was shown to be completely folded and thus enzymati cally active immediately upon release from the ribosome [Kolb et al. ( 1994) EMBO J. 13, 3631-3637]. However, no luciferase activity was obse rved while full-length luciferase was attached to the ribosome as a pe ptidyl-tRNA, probably because the C-terminal portion of the enzyme is masked by the ribosome and/or ribosome-associated proteins, Here we ha ve demonstrated that the ribosome-bound enzyme acquires the enzymatic activity when its C-terminus is extended by at least 26 additional ami no acid residues, The results demonstrate that the acquisition of the final native conformation by a nascent protein does not need the relea se of the protein from the ribosome.