Final answer:
Proteolytic cleavage of ORF1a/b leads to the degradation of the target protein into short peptides and eventually free amino acids, which is a key aspect of protein regulation and cellular metabolism.
Step-by-step explanation:
When ORF1a/b is proteolytically cleaved, the target protein is broken down into short peptide fragments by proteolytic enzymes such as those in the proteasome core.
This breakdown is part of post-translational processing which also includes the hydrolytic removal of N-terminal amino acids from polypeptides, as occurs with the removal of the formyl group and methionine in E. coli.
ORF1 is an unusual open reading frame present between the tRNATrp (A73) and TrpRS-A1 genes in bacteria and archaea, and it is predicted to be a structural homolog of class I aminoacyl-tRNA synthetases (aaRS) due to its conserved motifs and possible structural homology indicated by SWISS-MODEL predictions.
As the proteasome digests proteins to peptides and ultimately into free amino acids, this is a critical part of cellular metabolism and protein regulation.