Protease degradation of Autographa californica nuclear polyhedrosis virus proteins.

The Autographa californica nuclear polyhedrosis virus (Ac-NPV) occlusion bodies produced in vivo contained a protease which degraded occlusion body matrix protein and polypeptides of enveloped nucleocapsids during alkaline dissolution. The protease activity was required for complete dissociation of occlusion body matrix protein from the viral membrane during alkali liberation of the virus from occlusion bodies. In addition protease activity was required for the subsequent removal of the viral membrane from the nucleocapsids by Nonidet P40 treatments. Protease activity was not detected in occlusion bodies isolated from tissue culture cells or heat-treated (80 degrees , 45 min) occlusion bodies isolated from insect larvae. When occluded Ac-NPV virions were purified in the absence of protease activity, 26- polypeptides with molecular weights ranging from 115,000 to 15,000 were identified. The occlusion body matrix protein had an apparent molecular weight of 33,000.