EXPRESSION AND CHARACTERIZATION OF A RECOMBINANT MURINE CORONAVIRUS 3C-LIKE PROTEINASE

The replication of coronaviruses involves proteolytic processing of th e gene 1 translation products, pp1a and pp1ab. One of the key enzymes in this process is predicted to be a virus-encoded 3C-like proteinase. In this report, we describe a bacterial system that has allowed us to express and characterize a recombinant murine coronavirus (MHV-JHM) 3 C-like proteinase. The partially purified protein has been shown to ex hibit proteolytic activity in trans and mutation analysis has been use d to demonstrate the indispensability of Cys-3495 for enzymatic activi ty. Finally, the effect of class-specific proteinase inhibitors on the trans cleavage activity of the MHV 3C-like proteinase has been used t o demonstrate the functional and structural homology of this enzyme to the picornavirus 3C proteinases.