Autoradiography after Tricine-SDS-PAGE separation of the peptides formed by digestion of [14C]BG-inactivated CYP3A4 with CNBr or Lys C. The SDS-PAGE of the reconstituted system, the digestion of CYP3A4, and Tricine-SDS-PAGE of the digested peptides were carried out as described under Materials and Methods. Lane A, separation of peptides from CNBr cleavage; lane B, separation of peptides from Lys C cleavage; lane C, molecular weight markers.