Structural Determinants of High-Affinity Binding of Ryanoids to the Vertebrate Skeletal Muscle Ryanodine Receptor: A Comparative Molecular Field Analysis

Ryanodine receptor point mutant E4032A reveals an allosteric interaction with ryanodine

“…Our binding data, which show the discernable, although reduced, high-affinity binding of [ 3 H]ryanodine to the E4032A mutant, also suggest that this site is intact. Our hypothesis that ryanodine binds to allosteric sites is supported by molecular modeling studies, indicating that steric and electrostatic components of ryanodine derivatives (which may be expected to alter RyR calcium permeability) are not correlated with their ability to affect native RyR function (7,12,13). Thus, our results with the E4032A mutant channel suggest that ryanodine does not act as a pore blocker but instead, that ryanodine binding sites reside outside of the permeation pore, and that ryanodine binding to these sites has allosteric effects on calcium permeability.…”

“…Thus, compounds that open the channel increase the affinity for ryanodine caused by the opening of the pore to which ryanodine binds; ryanodine bound to the pore can occlude passage of Ca 2ϩ through the RyR. However, this hypothesis has not been tested directly, and recent molecular modeling studies have suggested that ryanodine may be acting at allosteric sites (12,13).…”

Ryanoids and related compounds. Identification of five new ryanoids from the plantRyaniaspeciosaVahl. Formal total syntheses of 3-deoxyryanodol (cinnzeylanol), 10-O-acetyl-3-deoxyryanodol (cinnzeylanine), 2-deoxyryanodol, 2-deoxy-2-epiryanodol, 2,3-dideoxy-2,3-dihydroryanodol, 2-deoxy-3-epiryanodol, and 2-deoxy-3-epiryanodine

“…Rapid exo-protonation at C2 of the resulting enolate 17A would then give cyclopentanone 17B, which would be reduced by lithium and protonated to give the most stable 3-exo hydroxyl group, with "anti" substituents at positions 2 and 3. Selective acylation of the 3-epi-hydroxyl group of 18 with 2-pyrrolecarboxylic acid (34) furnished 2-deoxy-3-epiryanodine (19).…”

“…We have also modified the oxidation level of ring A of in the ryanodine skeleton, which resulted in the syntheses of two (41.~ In a search to identify the structural features that are necnatural diterpenes, cinnzeylanol (14) and cinnzeylanine (15) essary to maintain biological activity, we (5-7) and (8-(25, 26), and of several other compounds (16,(18)(19)(20)21). 14) have recently focused on the characterization of new ryanoids from the plant Ryania speciosa Vahl, and also on skeleton and functional group modifications (5,6,8,10,(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) in order to obtain more information on their eventual role in the affinity of these molecules to the ryanodine binding site. tion time and were first obtained as a 1:5 mixture.…”

Chemical Conversion of Ryanodol to Ryanodine

“…[11][12][13][14] Compound 2 is a diterpenoid containing the exceedingly complex five fused rings (ABCDE-rings) with eleven contiguous stereocenters. Interestingly, the affinity of 2 toward RyRs of vertebrate skeletal muscle is 1700 times weaker than that of 1 (K D =7 nM), [15][16][17] demonstrating that the pyrrole group is a primary determinant for strong interactions of 1. Because of its important biological activities and intriguing structural features, many studies attempting the chemical construction of 1 has been carried out, which resulted in the total syntheses of ryanodol (2) by the Deslongchamps group in 1979 18,19) and by our laboratory in 2014.…”