Arginyl and histidyl groups are essential for organic anion exchange in renal brush-border membrane vesicles.

摘要: The effect of side chain modification on the organic anion exchanger in renal brush-border membrane was examined to identify what amino acid residues constitute substrate binding site. One histidyl-specific reagent, diethyl pyrocarbonate (DEPC), and 2 arginyl-specific reagents, phenylglyoxal 2,3-butanedione, were tested for their specifically mediated transport p-amino[3H]hippurate (PAH), a prototypic anion. refers difference uptake [3H]PAH absence presence known competitive inhibitor, probenecid, vesicles isolated from outer cortex canine kidneys. experiments performed utilizing rapid filtration assay. DEPC, phenylglyoxal, 2,3-butanedione inactivated PAH transport, i.e. probenecid inhibitable with IC50 values 160, 710, 1780 microM, respectively. rates inactivation by DEPC suggestive multiple pseudo first-order reaction kinetics consistent mechanism whereby more than 1 arginyl or histidyl residue is inactivated. Furthermore, (5 mM) did not affect rate inactivation. In contrast, affected specific since could be restored treatment hydroxylamine. results demonstrate that are essential vesicles. We conclude constitutes cationic site anionic substrate, whereas residue(s) serves guide away