We have cloned cDNAs that encode a complete open reading frame for a calcium channel alpha1 subunit from Drosophila melanogaster. The deduced 1851 amino acid protein belongs to the superfamily of voltage-gated sodium and calcium channels. Phylogenetic analysis shows that the sequence of this subunit is relatively distant from sodium channel alpha subunits and most similar to genes encoding the A, B, and E isoforms of calcium channel alpha1 subunits. To indicate its similarity to this subfamily of vertebrate isoforms, we name this protein Dmca1A, for Drosophila melanogaster calcium channel alpha1 subunit, type A. Northern blot analysis detected a single 10. 5 kb transcript class that is regulated developmentally, with expression peaks in the first larval instar, midpupal, and late pupal stages. In late-stage embryos, Dmca1A is expressed preferentially in the nervous system. Variant transcripts are generated by alternative splicing. In addition, single nucleotide variations between cDNAs and genomic sequence are consistent with RNA editing. Dmca1A maps to a chromosomal region implicated in, and is the likely candidate for, the gene involved in the generation of behavioral, physiological, and lethal phenotypes of the cacophony, nightblind-A, and lethal(1)L13 mutants.
