BETA-GALACTOSIDASE CONTAINING A HUMAN-IMMUNODEFICIENCY-VIRUS PROTEASE CLEAVAGE SITE IS CLEAVED AND INACTIVATED BY HUMAN-IMMUNODEFICIENCY-VIRUS PROTEASE

A 'cleavage cassette' specifying a decapeptide human immunodeficiency virus (HIV) protease cleavage site was introduced into six different locations of β-galactosidase (β-D-galactoside galactohydrolase, EC 3.2.1.23) in Escherichia coli. Four of these constructs retained β-galactosidase activity despite the insertion of the cleavage cassette. Of these four constructs, one was cleaved by HIV protease, resulting in the inactivation of β-galactosidase both in vivo and in vitro. This cleavage was inhibited by pepstatin A, a known inhibitor of HIV protease. Thus, β-galactosidase has been converted into an easily assayed substrate for HIV protease. An analogous construct of β-galactosidase containing a polio protease cleavage site was cleaved likewise by polio protease, suggesting that this system may be generic for monitoring cleavage by a variety of proteases.