Abstract
We describe two Drosophila melanogaster transcription units that are highly homologous to a ran Na+-channel proteins. One of these maps to the second chromosome and is identical to a Na+-channel gene whose partial sequence has been previously reported [Salkoff, L., Butler, A., Wei. A., Scavarda, N., Giffen, K., Ifune, L., Goodman, R. and Mandel, G. (1987) Science 237, 744-749]. The other transcription unit maps to position 14C/D, on the X chromosome, close to the paralyzed (para) gene. Mutations in para affect membrane excitability in Drosophila neurons [Ganetzky, B. and Wu. C. F. (1986) Annu. Rev. Genet. 20, 13-44]. Sequence comparisons suggest that two Na+-channel genes arose early in evolution, before the divergence of vertebrate and invertebrate lines.