sentence: However , a difference was observed between SUR2A and SUR1 residues as the basal current of SUR1 was 12-fold higher than SUR2A ( Fig. 2D ) suggesting that the MRP1 VFY residues disturbed less the SUR1 / Kir6.2 interaction than the SUR2A / Kir6.2 and yielded a stronger surface expression .