Selective determinants of inositol 1,4,5-trisphosphate and adenophostin A interactions with type 1 inositol 1,4,5-trisphosphate receptors.

Adenophostin A (AdA) is a potent agonist of inositol 1,4,5-trisphosphate receptors (IP(3) R). AdA shares with IP(3) the essential features of all IP(3) R agonists, namely structures equivalent to the 4,5-bisphosphate and 6-hydroxyl of IP(3) , but the basis of its increased affinity is unclear. Hitherto, the 2'-phosphate of AdA has been thought to provide a supra-optimal mimic of the 1-phosphate of IP(3) . We examined the structural determinants of AdA binding to type 1 IP(3) R (IP(3) R1). Chemical synthesis and mutational analysis of IP(3) R1 were combined with (3) H-IP(3) binding to full-length IP(3) R1 and its N-terminal fragments, and Ca(2+) release assays from recombinant IP(3) R1 expressed in DT40 cells. Adenophostin A is at least 12-fold more potent than IP(3) in functional assays, and the IP(3) -binding core (IBC, residues 224-604 of IP(3) R1) is sufficient for this high-affinity binding of AdA. Removal of the 2'-phosphate from AdA (to give 2'-dephospho-AdA) had significantly lesser effects on its affinity for the IBC than did removal of the 1-phosphate from IP(3) (to give inositol 4,5-bisphosphate). Mutation of the only residue (R568) that interacts directly with the 1-phosphate of IP(3) decreased similarly (by ~30-fold) the affinity for IP(3) and AdA, but mutating R504, which has been proposed to form a cation-π interaction with the adenine of AdA, more profoundly reduced the affinity of IP(3) R for AdA (353-fold) than for IP(3) (13-fold). The 2'-phosphate of AdA is not a major determinant of its high affinity. R504 in the receptor, most likely via a cation-π interaction, contributes specifically to AdA binding.

Rossi AM ，Sureshan KM ，Riley AM ，Potter VL ，Taylor CW ... -  《-》

Stimulation of inositol 1,4,5-trisphosphate (IP3) receptor subtypes by adenophostin A and its analogues.

Saleem H ，Tovey SC ，Riley AM ，Potter BV ，Taylor CW ... -  《PLoS One》

Contribution of phosphates and adenine to the potency of adenophostins at the IP₃ receptor: synthesis of all possible bisphosphates of adenophostin A.

Sureshan KM ，Riley AM ，Thomas MP ，Tovey SC ，Taylor CW ，Potter BV ... -  《-》

Binding of inositol 1,4,5-trisphosphate (IP3) and adenophostin A to the N-terminal region of the IP3 receptor: thermodynamic analysis using fluorescence polarization with a novel IP3 receptor ligand.

Ding Z ，Rossi AM ，Riley AM ，Rahman T ，Potter BV ，Taylor CW ... -  《-》

Determinants of adenophostin A binding to inositol trisphosphate receptors.

Morris SA ，Nerou EP ，Riley AM ，Potter BV ，Taylor CW ... -  《-》