Effect of cycloheximide on viral precursor protein B in Sindbis virus-infected BHK cells

The possible role of B protein, a postulated precursor of viral envelope proteins was studied in Sindbis virus-infected BHK cells. Although tryptic digestion of the B protein produces tryptic peptides of the viral envelope proteins it seems unlikely that B molecules accumulated in the cytoplasm of infected cells are subsequently cleaved into structural proteins. We suggest that if B is really the precursor of E1 and PE2 viral envelope proteins, the cleavage takes place on the ribosomes during the synthesis of the second part of the B protein. Low concentrations of cycloheximide completely blocked the synthesis of B protein but did not inhibit the synthesis of viral structural proteins.