Cleavage of recombinant and cell derived human immunodeficiency virus 1 (HIV-1) Nef protein by HIV-1 protease.

Recombinant purified Nef protein of HIV-1, as well as Nef protein derived from extracts of permanently HIV-1 infected glioblastoma cells and monocytes, are specifically cleaved by the HIV-1 protease. Nef cleavage products in cellular extracts treated with protease showed identical molecular weights as those obtained by digestion of purified Nef with recombinant HIV-1 protease. Since cellular extracts were prepared by detergent and mechanical lysis it cannot be excluded that physiological cytoplasmic conditions were altered. The lack of Nef cleavage by endogenous HIV-1 protease in infected cells might be due to low concentrations of viral protease and the presence of Gag precursor molecules as natural substrate. Using a panel of monoclonal antibodies two cleavage fragments of 19 kDa and 8 kDa were defined. The cleavage site was located by microsequencing between amino acid 57 and 58 (AW*LEAQEEEEVGF). The conserved cleavage motif within HIV-1 Nef suggests a potential biological function of Nef processing.