Use of recombinant P-glycoprotein fragments to produce antibodies to the multidrug transporter.

Multidrug-resistance of human cancer cells may result from expression of a 170,000 dalton multidrug efflux pump called P-glycoprotein. To identify this multidrug transporter, and to study its structure and function, we have generated polyclonal rabbit antibodies against the amino-terminal and carboxy-terminal halves of the molecule using recombinant protein fragments produced in Escherichia coli. Two recombinant P-glycoprotein fragments, representing amino acids 140-228 and 919-1280, were overproduced in Escherichia coli by an inducible T7 expression system, gel-purified and injected into rabbits. Both antisera specifically immunoprecipitate 3H-azidopine and 35S-methionine labeled P-glycoprotein from multidrug-resistant cells and detect P-glycoprotein on Western blots with high sensitivity. Because these antisera were raised against epitopes in the amino- and carboxy-terminal halves of P-glycoprotein, they should be useful as research tools to define the function of these two halves of the molecule.