Fig. 11. Autoradiograms of PCTV-budding reactions showing the 9-kDa band to be phosphorylated only during active PCTV budding. The 9-kDa band is absent in liver and kidney ER. PCTV-budding reactions were performed as described for Fig. 1; proteins were separated by 15% SDS-PAGE and autoradiographed. (A) Complete reaction except that the cytosol was either mock immunodepleted using IgG (lane 1) or immunodepleted of Sar1 (lane 2). The ER had been washed with 2 M urea (Materials and Methods). (B) PCTV-budding reaction using ER treated with the indicated antibodies (lane 1, IgG; lane 2, anti-apoB48; lane 3, anti-rBet1; lane 4, anti-Sec22b; lane 5, anti-VAMP7 antibodies). Excess antibodies were removed by washing. Post incubation proteins were separated by 8%-16% SDS-PAGE and autoradiographed. (C) ER and cytosol from intestine (lanea1, 2), liver (lanes 3, 4) and kidney (lanes 5, 6) were incubated with the complete budding reaction mix as described for Fig. 9. In each lane, 30 µg of protein were separated by 15% SDS-PAGE and autoradiographed.