Modification of the mitochondrial sulfonylurea receptor by thiol reagents

The purpose of this study was to investigate the effects exerted by thiol-m odifying reagents on themitochondrial sulfonylurea receptor. The thiol-oxid izing agents (timerosal and 5,5'-dithio-bis (2-nitrobenzoic acid)) were fou nd to produce a large inhibition (70% to 80%) of specific binding of [H-3]g libenclamide to the beef heart mitochondrial membrane. Similar effects were observed with membrane permeable (N-ethylmaleimide) and non-permeable (mer salyl) thiol modifying agents. Glibenclamide binding was also decreased by oxidizing agents (hydrogen peroxide) but not by reducing agents (reduced gl uthatione, dithiothreitol and the 2,3-dihydroxy-1,4-dithiolbutane), The res ults suggest that intact thiol groups, facing the mitochondrial matrix, are essential for glibenclamide binding to the mitochondrial sulfonylurea rece ptor. (C) 1999 Academic Press.