THE EFFECTS OF AMINO ACID-REACTIVE REAGENTS ON THE FUNCTIONING OF THE INOSITOL 1,4,5-TRISPHOSPHATE-SENSITIVE CALCIUM-CHANNEL FROM RAT CEREBELLUM

Covalent modification of arginine residues with phenylglyoxal and lysine residues with 4,4'-diisothiocyano-2,2'-disulphonic acid stilbene (DIDS) was carried out in preparations of rat cerebellar microsomes, as was the interaction of silver ions (silver nitrate) with cysteine residues. The effects of these amino acid-reactive agents on [H-3]inositol 1,4,5-trisphosphate (InsP3) binding and InsP3-induced calcium release were assessed. Both phenylglyoxal and DIDS inhibited [H-3]InsP3 binding and InsP3-induced calcium release (IC50 = 2.0 mM and 18 muM, respectively). Silver ions inhibited InsP3-induced Ca2+ release alone (IC50 almost-equal-to 1 muM). These results suggest that arginine and lysine residues may be located at or close to the InsP3 binding site of the InsP3 receptor, while cysteine residues are important in channel opening.