Deletion of amino acids 1641-2437 from the foot region of skeletal muscle ryanodine receptor alters the conduction properties of the Ca release channel.
The ryanodine receptor (RyR) of skeletal muscle contains two functional domains: a carboxyl-terminal hydrophobic domain that forms the putative conduction pore of the calcium release channel, and a large cytoplasmic domain that corresponds to the "foot structure." To understand the contribution of the foot structure to the function of the calcium release channel, we studied a RyR deletion mutant, delta(1641-2437)-RyR, in which a region that is rich in glutamate and aspartate residues (a.a. 1641-2437) was removed. The wild-type and delta(1641-2437)-RyR proteins were expressed in a Chinese hamster ovary (CHO) cell line, and functions of single calcium release channels were measured in the lipid bilayer membrane. The wild-type RyR forms functional calcium release channels with a linear current-voltage relationship similar to that of the native channel identified in the sarcoplasmic reticulum membrane of skeletal muscle, whereas the channels formed by delta(1641-2437)-RyR exhibit significant inward rectification, i.e., currents moving from cytoplasm into SR lumen were approximately 20% less than that in the opposite direction. As in to the wt-RyR channel, opening of the delta(1641-2437)-RyR channel has a bell-shaped dependence on the cytoplasmic calcium, but the calcium-dependent activation and inactivation processes of the delta(1641-2437)-RyR channel are shifted to higher calcium concentrations. Our data show that deletion of a.a. 1641-2437 from the foot region of the skeletal muscle RyR results in changes in both ion conduction and calcium-dependent regulation of the calcium release channel.
Bhat
M B
MB
Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA.
Zhao
J
J
Hayek
S
S
Freeman
E C
EC
Takeshima
H
H
Ma
J
J
D000818:Animals; D001224:Aspartic Acid; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry* / Q000502:physiology*; D003001:Cloning, Molecular; D006224:Cricetinae; D018698:Glutamic Acid; D007425:Intracellular Membranes / Q000502:physiology; D015640:Ion Channel Gating; D007700:Kinetics; D008051:Lipid Bilayers; D008564:Membrane Potentials; D008861:Microsomes / Q000502:physiology; D009124:Muscle Proteins / Q000737:chemistry* / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism*; D016296:Mutagenesis; D011336:Probability; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel; D017384:Sequence Deletion; D014162:Transfection
D015220:Calcium Channels; D008051:Lipid Bilayers; D009124:Muscle Proteins; D011994:Recombinant Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D001224:Aspartic Acid; D018698:Glutamic Acid; D002118:Calcium