CLONING OF A PUTATIVE VOLTAGE-GATED SODIUM-CHANNEL FROM THE TURBELLARIAN FLATWORM BDELLOURA-CANDIDA

The neuromuscular sodium currents of early invertebrates such as platy helminths display distinctive kinetic and pharmacological properties. We have cloned a cDNA from the horseshoe crab flatworm Bdelloura candi da that encodes a protein homologous to the primary subunit of voltage -gated sodium channels. The B. candida protein, named BdNa1, exhibits amino acid identity of 40-47% to sodium channels of vertebrates and hi gher invertebrates. BdNa1 has the multidomain structure characteristic of sodium channels, and is most highly conserved in the hydrophobic t ransmembrane segments and the regions that form the pore of the channe l. Northern blot analysis confirms the presence of a 5.4 kb BdNa1 tran script in B. candida tissue. The information provided by analysis of t he BdNa1 sequence offers insight into the physiology of platyhelminth sodium currents.