Expression and characterization of human foamy virus proteinase

The human foamy virus proteinase was expressed in fusion with maltose bindi ng protein in Escherichia coli and purified. The specific activity of the f usion protein was similar to that of the processed enzyme. The kinetic cons tants on foamy virus cleavage site substrates were very low but comparable to those obtained with the gag-encoded avian proteinase on its own substrat es. The proteinase showed preference for high ionic strength and a pH optim um of 6.6. None of the tested retroviral cleavage site peptides were substr ates, however, some peptides representing cleavage sites in retrotransposon s were properly processed by the enzyme. (C) 1999 Federation of European Bi ochemical Societies.