Specific residues in the putative pore helix, selectivity filter, and S6 transmembrane helix of
the inositol 1, 4, 5-trisphosphate receptor were mutated in order to examine their effects on
channel function. Mutation of 5 of 8 highly conserved residues in the pore helix/selectivity
filter region inactivated the channel (C2533A, G2541A, G2545A, G2546A, and G2547A). Of
the remaining three mutants, C2527A and R2543A were partially active and G2549A
behaved like wild type receptor. Mutation of a putative glycine hinge residue in the S6 helix …