Abstract
A human brain alpha 1 Ca2+ channel subunit was cloned and expressed in Xenopus laevis oocytes. The open reading frame, encoding 2,312 amino acids, has high homology to the marine ray doe-1, the rat E-type, and the rabbit brain BII alpha 1 subunits. The amino and carboxy termini of this human.E-type alpha 1 subunit (alpha 1E) are most similar to the rabbit BII-1 splice variant, the remainder being colinear with the BII alpha 1 with the exception of two insertions, one of 43 amino acids in the C-terminus and another of 7 amino acids, found also in the rat alpha 1E, between domains II and III. Two potential Ca2+ binding sites are predicted from its primary structure. The expression of inward Ba2+ currents reveals voltage-dependent activation and inactivation measured by the cut-open oocyte vaseline-gap technique, with kinetics that correspond to that of a high-voltage-activated neuronal Ca2+ channel, and pharmacologic properties that resemble those of some low-voltage-activated neuronal Ca2+ currents. The human alpha 1E currents are insensitive to omega-conotoxin-GVIA (1 microM), omega-agatoxin-IVA (200 nM), a synthetic funnel web spider toxin (FTX, 20 microM), and Bay-K8644 (0.5 microM); they are inhibited 20% by high concentrations of methoxyverapamil and diltiazem, 65% by 0.1% crude funnel web spider venom and 100% by Ni2+ (IC50 = 30 nM). Single-channel records show a complex activity pattern with several apparent conductance states, the largest having a conductance of 14 pS.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / pharmacology
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Alternative Splicing
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Amino Acid Sequence
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Animals
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Barium / pharmacology
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Base Sequence
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Binding Sites
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Brain / metabolism*
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Calcium / metabolism
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Calcium Channel Blockers / pharmacology
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Calcium Channels / biosynthesis*
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Calcium Channels / chemistry
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Calcium Channels / physiology
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Calcium Channels, R-Type
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Cation Transport Proteins*
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Cloning, Molecular
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DNA Primers
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Diltiazem / pharmacology
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Female
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Gallopamil / pharmacology
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Gene Expression*
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Genetic Variation
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Humans
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Kinetics
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Macromolecular Substances
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Membrane Potentials / drug effects
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Molecular Sequence Data
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Neurons / metabolism*
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Nickel / pharmacology
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Oocytes / drug effects
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Oocytes / physiology*
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Peptides / pharmacology
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Polyamines / pharmacology
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Polymerase Chain Reaction
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Rabbits
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Rats
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Restriction Mapping
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Sequence Homology, Amino Acid
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Skates, Fish
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Spider Venoms / pharmacology
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Xenopus laevis
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omega-Agatoxin IVA
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omega-Conotoxin GVIA
Substances
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CACNA1E protein, human
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Cacna1e protein, rat
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Calcium Channel Blockers
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Calcium Channels
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Calcium Channels, R-Type
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Cation Transport Proteins
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DNA Primers
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FTX, spider toxin
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Macromolecular Substances
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Peptides
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Polyamines
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Spider Venoms
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omega-Agatoxin IVA
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Barium
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Gallopamil
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3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester
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Nickel
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omega-Conotoxin GVIA
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Diltiazem
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Calcium