Lawson M A, Semler B L
Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine 92717.
Proc Natl Acad Sci U S A. 1991 Nov 15;88(22):9919-23. doi: 10.1073/pnas.88.22.9919.
The picornavirus 3C proteinases are substrate-specific thiol proteases that have been shown by secondary structure predictions and protein modeling studies to be similar to the trypsin-like serine proteases. We have examined several mutations of the 3C proteinase at putative active site and non-active site residues. The effect on 3C-mediated protein processing supports the model of serine protease similarity. In particular, we have shown that 3C can utilize a serine at position 147, which is predicted to supply the nucleophilic residue of the catalytic triad. We suggest that picornavirus 3C proteinases may represent a class of enzymes that have maintained the catalytic mechanism characteristic of a proposed enzyme ancestral to the highly divergent class of serine proteases.
