The 30 S lobster skeletal muscle Ca2+ release channel (ryanodine receptor) has functional properties distinct from the mammalian channel proteins.
The 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (Chaps)-solubilized ryanodine receptor (RyR) of lobster skeletal muscle has been isolated by rate density centrifugation as a 30 S protein complex. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the purified 30 S receptor revealed a single high molecular weight protein band with a mobility intermediate between those of the mammalian skeletal and cardiac M(r) 565,000 RyR polypeptides. Immunoblot analysis showed no or only minimal cross-reactivity with the rabbit skeletal and canine cardiac RyR polypeptides. By immunofluorescence the lobster RyR was localized to the junctions of the A-I bands. Following planar lipid bilayer reconstitution of the purified 30 S lobster RyR, single channel K+ and Ca2+ currents were observed which were modified by ryanodine and optimally activated by millimolar concentrations of cis (cytoplasmic) Ca2+. Vesicle-45Ca2+ flux measurements also indicated an optimal activation of the lobster Ca2+ channel by millimolar Ca2+, whereas 45Ca2+ efflux from mammalian skeletal and cardiac muscle sarcoplasmic reticulum (SR) vesicles is optimally activated by micromolar Ca2+. Further, mammalian muscle SR Ca2+ release activity is modulated by Mg2+ and ATP, whereas neither ligand appreciably affected 45Ca2+ efflux from lobster SR vesicles. These results suggested that lobster and mammalian muscle express immunologically and functionally distinct SR Ca2+ release channel protein complexes.
Seok
J H
JH
Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill 27599-7260.
Xu
L
L
Kramarcy
N R
NR
Sealock
R
R
Meissner
G
G
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D015151:Immunoblotting; D007700:Kinetics; D008322:Mammals; D008564:Membrane Potentials / Q000187:drug effects; D008970:Molecular Weight; D009132:Muscles / Q000502:physiology*; D008121:Nephropidae; D011950:Receptors, Cholinergic / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*; D012433:Ryanodine / Q000378:metabolism / Q000494:pharmacology*; D019837:Ryanodine Receptor Calcium Release Channel
D015220:Calcium Channels; D011950:Receptors, Cholinergic; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D002118:Calcium