s-HJV does not originate from isolated membranes. Membrane fractions from WT HJV-transfected HeLa cells were incubated for 18 hours at 4°C and 37°C and centrifuged; the corresponding supernatants and membrane pellets were separated by 10% SDS-PAGE under reducing conditions. Right panel shows the same overexposed film. Proteins were revealed using anti-HJV. mm indicates microsomal membranes; sn, supernatant. The relative molecular mass, in kilodaltons, is indicated on the left.