Calcium dependent activation of skeletal muscle Ca2+ release channel (ryanodine receptor) by calmodulin.
In this study terminal cisternae vesicles from rabbit skeletal muscle were fused into planar bilayers and the effect of calmodulin on single Ca2+ release channel currents was investigated. In the presence of 10(-7) and 10(-9) M free [Ca2+], nanomolar concentrations of calmodulin activated the channel by increasing the open probability of single-channel events in a dose dependent manner. The activatory effect of calmodulin was reversed by 10 microM ruthenium red. At 10(-5) M free [Ca2+], calmodulin (0.1-1 microM) inhibited channel activity. Calmodulin overlays were carried out using concentrations of Ca2+ similar to those used for the planar lipid bilayer assays. In the presence of 10(-7) M [Ca2+], calmodulin bound to the ryanodine receptor, to a region defined by residues 2937-3225 and 3546-3655. These results suggest that calmodulin may activate the Ca(2+)-release channel (ryanodine-receptor) by interacting with binding sites localized in the central portion of the RYR protomer.
Buratti
R
R
Istituto di Cibernetica e Biofisica, CNR, Genova, Italy.
Prestipino
G
G
Menegazzi
P
P
Treves
S
S
Zorzato
F
F
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002147:Calmodulin / Q000494:pharmacology*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D008051:Lipid Bilayers; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D011817:Rabbits; D012430:Ruthenium Red / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel
D015220:Calcium Channels; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D008051:Lipid Bilayers; D009124:Muscle Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D012430:Ruthenium Red; D002118:Calcium