GENOMIC STRUCTURE OF A POTASSIUM CHANNEL TOXIN FROM HETERACTIS-MAGNIFICA

We provide information on the gene encoding the K+ channel toxin, HmK, of the sea anemone Heteractis magnifica. A series of DNA amplificatio ns by PCR, which included the amplification of the 5'-untranslated reg ion of the gene, showed that an intron of 402 nucleotides separated th e sequence that encodes the matured toxin front the signal peptide seq uence, A second 264 nucleotide intron interrupted the 5'-untranslated region of the previously reported HmK cDNA, Two possible transcription -initiation sites were identified by primer extension analysis, Corres ponding TATA-box consensus sequences, characteristic of a promoter reg ion, were also located from PCR products of uncloned libraries of adap tor-ligated genomic DNA fragments, The coding region for matured HmK i s intronless, The same is also true for other sea anemone toxins repor ted thus far, More notably, a similar intron-exon organization is pres ent in other ion channel-blocking toxins from scorpions implying that molecules having similar functions share a similar organization at the genomic level suggesting a common path of evolution. (C) 1997 Federat ion of European Biochemical Societies.