INVESTIGATIONS ON THE SUBSTRATE SPECIFICITY AND INHIBITION OF THE PROTEINASE OF EQUINE INFECTIOUS ANEMIA VIRUS

Abstract

The proteinase of the equine infectious anemia virus was purified from concentrated virus to apparent homogeneity. The purified proteinase was utilized for kinetic studies. The substrate binding pocket of the proteinase was found to be somewhat more extended (recognizing 8-9 residues of the substrate) than that of human immunodeficiency virus proteinases (recognizing 6-7 residues). The equine infectious anemia virus proteinase recognized synthetic peptides representing the naturally occurring cleavage site in the Gag and Gag- Pol polyproteins of its own naturally occurring cleavage sites and those of human immunodeficiency virus sites. Oligopeptides representing naturally occurring cleavage sites of the transmembrane and reverse transcriptase proteins were also correctly hydrolyzed by the proteinase. Several substrate based inhibitors originally developed against human immunodeficiency virus proteinase and available from previous studies were studied using the partially purified equine infectious anemia virus proteinase. Out of the thirteen inhibitors, five phosphinic acid isosters and one hydroxyethylene isostere were found to be inhibitory. The IC₅₀ ranged from 8uM to >20uM. In chronically infected cells, six inhibitors (out of fifteen tested) substantially inhibited mature (reverse transcriptase positive) virus production in cells chronically infected with an endogenous feline virus. Four of these also inhibited Friend-murine leukemia virus production in Eveline cells.