Radiation inactivation of multispecific transport systems for bile acids and xenobiotics in basolateral rat liver plasma membrane vesicles.
The functional molecular mass of the cholate, phallotoxin, iodipamide, and ouabain transport proteins in isolated basolateral plasma membrane vesicles was determined by radiation inactivation. Purified basolateral plasma membrane vesicles were irradiated (-90 to -120 degrees C) with high energy electrons from a 10-MeV linear accelerator at doses from 0 to 30 megarads. After each dose, the initial uptake, the equilibrium binding, and the binding of the substrates at 4 degrees C were checked. The size of the transporting function was, for cholate, 107 +/- 8.9 kDa; for phallotoxin, 104 +/- 7 kDa; and for ouabain, 120 +/- 4.7 kDa. The target size for the binding proteins was 56 +/- 4.2, 57 +/- 5, and 47.2 +/- 1.95 kDa for cholate, phallotoxin, and taurocholate, respectively. In the case of iodipamide, the functional molecular mass for both the transport and binding proteins was 54 +/- 4.8 kDa.