Surface plasmon resonance studies prove the interaction of skeletal musclesarcoplasmic reticular Ca2+ release channel/ryanodine receptor with calsequestrin

A high affinity molecular interaction is demonstrated between calsequestrin and the sarcoplasmic reticular Ca2+ release channel/ryanodine receptor (Ry R) by surface plasmon resonance, K-D values of 92 nM and 102 nM for the pho sphorylated and dephosphorylated calsequestrin have been determined, respec tively. Phosphorylation of calsequestrin seems not to influence this high a ffinity interaction, i.e. calsequestrin might always be bound to RyR. Howev er, the phosphorylation state of calsequestrin determines the amount of Ca2 + released from the lumen. Dephosphorylation of approximately 1% of the pho sphorylated calsequestrin could be enough to activate the RyR channel half- maximally, as we hale shown previously [Szegedi et al., Biochem. J. 337 (19 99) 19]. (C) 2000 Federation of European Biochemical Societies.