[The dynamics of the domains of the IP3-binding site of the inositol-1,4,5-triphosphate-sensitive calcium channel, induced by inositol-1,4,5-triphosphate and calcium].

The dynamics of the inositol-1,4,5-triphosphate-sensitive calcium channel after binding of inositol-1,4,5-triphosphate and Ca2+ was analyzed by the Monte Carlo minimization technique. It was shown that the binding of Ca2+ with the unliganded receptor (channel) leads to a turning of the beta-sheet domain relative to the alpha-helical domain with the formation of the receptor conformation that is open for the entry of ions into the cytoplasmic channel vestibule, sterically closed for their passage through the vestibule in the part adjacent to the alpha-helical domains, and unfavourable for subsequent binding of inositol-1,4,5-triphosphate with the receptor. When both co-agonists bind to the receptor, the structure rearrangements induced eliminate both these steric obstacles for the passage of ions through the IP3-binding domain: one at the entrance of the channel cytoplasmic vestibule and the other that is placed deeper in the vestibule near the alpha-domains. The role of the dynamics of the receptor binding core in the IP3-sensitive channel gating is discussed.