Analyses of levels of GaLV Env Pr85 precursor and SU subunit. A. Schematic representation of FLAG-tagged GaLV Env, showing precursor (Pr85), mature SU and TM subunits, signal peptide (SP) and R peptide (R). B. Representative Western blots and quantitative analysis of ratio of levels of FLAG-tagged GaLV Env Pr85 precursor and SU subunit, in presence of pHR' and either control plasmid pGEM, or packaging plasmids R8.2, R8.91 or R8.2ΔVpu. Samples were deglycosylated with either PGNase F or endoH prior to SDS-PAGE, and analyzed by immunoblotting with anti-FLAG antibody.