Abstract: A yeast host which can express P-glycoprotein, i.e., the product of MDR-related gene, in the cell membrane in the same state as observed in multidrug resistant cells produced by connecting the MDR-related gene which carries multidrug resistance to a yeast expression vector and transforming the yeast with said recombinant vector; a cell membrane fraction containing a substantial amount of P-glycoprotein produced by said yeast and a process for the preparation thereof; and a recombinant vector for expressing the MDR-related gene in a yeast host.