MOLONEY MURINE LEUKEMIA-VIRUS PROTEASE EXPRESSED IN BACTERIA IS ENZYMATICALLY ACTIVE

Replication of Moloney murine leukemia virus requires a readthrough tr anslation mechanism to generate the Gag-Pol polyprotein. One of the fi nal products of this polyprotein is the protease (PR), which is requir ed to generate the mature virion proteins. The assembly of Gag and Gag -Pol polyproteins into a virion followed by activation of the viral pr otease is necessary to produce a mature, infectious particle. These ev ents are believed to occur near the cell membrane just prior to the bu dding of the virion. We report here the autoproteolytic activity of th e viral PR when a Gag-PR fusion protein is expressed in E. coli. Effic ient cleavage at the p12/CA, CA/NC and NC/PR junctions was observed. T hus the Moloney murine leukemia virus PR is capable of cleaving its su bstrates in the absence of specific host factors.