Characterization of a papain-like cysteine-proteinase encoded by gene 1 of the human coronavirus HCV 229E.

Expression of the coronaviral gene 1 polyproteins, pp 1a and pp 1ab, involves a series of proteolytic events that are mediated by virus-encoded proteinases similar to cellular papain-like cysteine-proteinases and the 3C-like proteinases of picornaviruses. In this study, we have characterized, in vitro, the human coronavirus HCV 229E papain-like cysteine-proteinase PCP 1. We show that PCP 1 is able to mediate cleavage of an aminoterminal polypeptide, p9, from in vitro translation products representing the aminoproximal region of pp 1a/pp 1ab. Mutagenesis studies support the prediction of Cys1054 and His1278 as the catalytic amino acids of the HCV 229E PCP 1, since mutation of these residues abolishes the proteolytic activity of the enzyme.