“The L65R(TM1), T199R(TM3), I306R(TM5), or F343R(TM6) mutations were introduced into the P-gp mutant L339C(… carried out in the presence of various concentrations of vinblastine, cyclosporin A, or rhodamine B. The presence of arginine residues … vinblastine (L65R, T199R, and I306R), cyclosporin (…) by 4–60-fold.”