A negatively charged region of the skeletal muscle ryanodine receptor is involved in Ca2+-dependent regulation of the Ca2+ release channel

The ryanodine receptor/Ca2+ release channels from skeletal (RyR1) and cardi ac (RyR2) muscle cells exhibit different inactivation profiles by cytosolic Ca2+. D3 is one of the divergent regions between RyR1 (amino acids (aa) 18 72-1923) and RyR2 (aa 1852-1890) and may contain putative binding site(s) f or Ca2+-dependent inactivation of RyR, To lest this possibility, we have de leted the D3 region from RyR1 (Delta D3-RyR1), residues 1038-3355 frotn RyR 2 (Delta(1038-3355)-RyR2) and inserted the skeletal D3 into Delta(1038-3355 )-RyR2 to generate sD3-RyR2, The channels formed by Delta D3-RyR1 and Delta (1038-3355)-RyR2 are resistant to inactivation by mM [Ca2+], whereas the ch imeric sD3-RyR2 channel exhibits significant inactivation at mM [Ca2+]. The Delta D3-RyR1 channel retains its sensitivity to activation by caffeine, b ut is resistant to inactivation by Mg2+. The data suggest that the skeletal D3 region is involved in the Ca2+-dependent regulation of the RyR1 channel . (C) 1999 Federation of European Biochemical Societies.