Electrophoretic analysis of p-glycoproteins produced by mouse J774.2 and chinese hamster ovary multidrug-resistant cells

P-glycoprotein (P-gp) plays a fundamental role in multidrug resistance. The quantity of P-gp relates to the degree of drug resistance. A comparison was made between P-gps in mouse and hamster cell lines in both Laemmli and modified Fairbanks gel systems. Both proteins are derived from precursors of similar size that undergo differential N-linked glycosylation. The electrophoretic mobility and the amount of P-gp are remarkably dependent on the conditions of analysis. Notably, boiling P-gp before Laemmli gel elec-trophoresis decreases its mobility by an amount that is equivalent to ≈15 kDa and results in an apparent diminution in the amount of protein. The latter effect can give a false impression concerning the quantity of P-gp in cells.