FIGURE 3.

PAM-1/OSX is more sensitive to trypsin digestion than PAM-1. Membranes from PAM-1 and PAM-1/OSX AtT-20 cells were digested with increasing amounts of trypsin for 5 min at 37 °C. A, samples were assayed for PHM and PAL activity. B, after fractionation by SDS-PAGE, antibodies specific for PHM, PAL, and the cytosolic domain (CD) were used to identify major tryptic fragments. Representative blots are shown; the proteins that correspond to each numbered band are illustrated. 60K*, unique proteolytic product seen in PAM-1 cells; 68K#, cleavage product seen more in PAM-1/OSX cells. Graphs show the appearance of PHMcc and PALcc (band#3 and band#6, respectively) relative to PAM-1 in the control as a function of trypsin added; the experiment was repeated twice, with similar results.