Molecular cloning of a novel form (two repeat) protein related to voltage-gated sodium and calcium channels.

We report here the cloning of a novel protein from rat kidney that contains two domains (III), each with S1-S6 segments that are found in voltage-gated Ca and Na channels. Because of unusual structure, the protein was named two repeat ion channel 1 (TRC1). TRC1 encodes 819 amino acids with two conserved positively charged voltage sensor segments (S4) but the pore segments are not conserved. Northern blot analysis showed that TRC1 mRNA (5kb) was expressed widely. It was expressed at relatively high level in kidney, liver, and lung. Low levels of expression were observed in all other tissues. Based on its primary structure, we propose that TRC1 might be the predecessor of conventional four repeat voltage-gated Ca and Na channels.