NMR solution structure and conformational analysis of the calcium release agent cyclic adenosine 5 '-diphosphate ribose (cADPR)

A high-resolution NMR study of the solution structure of the calcium releas e agent cADPR has been performed. Pseudorotationals analysis reveals that i n solution both sugar rings in cADPR adopt predominantly (similar to 75%) S outh conformations, with the A and N rings adopting approximately T-2(3) C2 ' -endo(major)C3 ' -exo(minor) and T-4(3) (C3 ' -exo-C4 ' -endo) conformat ions, respectively. The backbone torsion angles beta and gamma have also be en determined. While the minor North conformers were not observed in the cr ystal structure of cADPR, the solution values of the major South conformers compare well to those found in crystal structure.