A putative voltage-gated sodium channel alpha subunit (PpSCN1) from the hydrozoan jellyfish, Polyorchis penicillatus: structural comparisons and evolutionary considerations.
Extant cnidarians are probably the simplest metazoans with discrete nervous systems and rapid, transient voltage-gated currents carried exclusively by Na+ ions. Thus cnidarians are pivotal organisms for studying the evolution of voltage-gated Na+ channels. We have isolated a full-length Na+ channel alpha subunit cDNA (PpSCN1) from the hydrozoan jellyfish, Polyorchis penicillatus, that has one of the smallest known coding regions of a four domain Na+ channel (1695 amino acids). Homologous residues that have a critical bearing on the selectivity filter, voltage-sensor and binding sites for tetrodotoxin and lidocaine in vertebrates and most invertebrates differ in cnidarians. PpSCN1 is not alternatively-spliced and may be the only pore-forming alpha subunit available to account for at least three electrophysiologically distinct Na+ currents that have been studied in P. penicillatus.
Spafford
J D
JD
Department of Biological Sciences, University of Alberta, Edmonton, Canada.
Spencer
A N
AN
Gallin
W J
WJ
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003063:Cnidaria / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D004594:Electrophysiology; D019143:Evolution, Molecular; D015640:Ion Channel Gating / Q000235:genetics*; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012333:RNA, Messenger / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000235:genetics*
D018076:DNA, Complementary; D012333:RNA, Messenger; C111680:SCN1 protein, Polyorchis penicillatus; D015222:Sodium Channels; D012964:Sodium