Protease of adenovirus type 2: Partial characterization

Abstract

An adenovirus-associated protease activity specific for the cleavage of core polypeptide PVII to polypeptide VII was identified and its properties were studied using an in vitro assay system. All temperature-sensitive (ts) mutants examined failed to induce protease activity at 39°. Activity was restored in revertants. The protease activity was completely inhibited by 1 m M tosylamide phenylethylchloromethyl ketone while phenylmethylsulfonylfluoride and tosyl-lysinechloromethyl ketone at 1 m M reduced enzyme activity to 36 and 10% of control, respectively. By contrast ethylenediamine tetraacetic acid had no effect. Optimum enzyme activity was observed at neutral pH. Enzyme activity was stable up to, but not beyond, 45°. Polypeptide PVII was cleaved whether it was in the soluble form, bound form, heat-, or acid-precipitated form. Wild-type young virions contain endogenous protease activity while the virions produced at 39° by tsl-infected cells do not. The PVII contained in these tsl-39 virions, however, may be processed by exogenous WT enzyme after the particles have been frozen-thawed several times. These results suggest that the adenovirus-associated protease is a chymotrypsin-like, nonmetalo, neutral protease.