Primary structure and functional expression of a mammalian skeletal muscle sodium channel.
We describe the isolation and characterization of a cDNA encoding the alpha subunit of a new voltage-sensitive sodium channel, microI, from rat skeletal muscle. The 1840 amino acid microI peptide is homologous to alpha subunits from rat brain, but, like the protein from eel electroplax, lacks an extended (approximately 200) amino acid segment between homologous domains I and II. Northern blot analysis indicates that the 8.5 kb microI transcript is preferentially expressed in skeletal muscle. Sodium channels expressed in Xenopus oocytes from synthetic RNA encoding microI are blocked by tetrodotoxin and mu-conotoxin at concentrations near 5 nM. The expressed sodium channels have gating kinetics similar to the native channels in rat muscle fibers, except that inactivation occurs more slowly.
Trimmer
J S
JS
Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510.
Cooperman
S S
SS
Tomiko
S A
SA
Zhou
J Y
JY
Crean
S M
SM
Boyle
M B
MB
Kallen
R G
RG
Sheng
Z H
ZH
Barchi
R L
RL
Sigworth
F J
FJ
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D015870:Gene Expression; D007700:Kinetics; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009132:Muscles / Q000378:metabolism*; D051381:Rats; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D015222:Sodium Channels / Q000378:metabolism*; D014158:Transcription, Genetic; D014981:Xenopus
D008565:Membrane Proteins; D015222:Sodium Channels; D004247:DNA