Functional expression of a probable Arabidopsis thaliana potassium channel in Saccharomyces cerevisiae

We report the isolation of a cDNA (KAT1) from Arabidopsis thaliana that encodes a probable K⁺ channel. KAT1 was cloned by its ability to suppress a K⁺ transport-defective phenotype in mutant Saccharomyces cerevisiae cells. This suppression is sensitive to known K⁺ channel blockers, including tetraethylammonium and Ba²⁺ ions. The KAT1 cDNA contains an open reading frame capable of encoding a 78-kDa protein that shares structural features found in the Shaker super-family of K⁺ channels. These include a cluster of six putative membrane-spanning helices (S1-S6) at the amino terminus of the protein, a presumed voltage-sensing region containing Arg/Lys-Xaa-Xaa-Arg/Lys repeats within S4, and the highly conserved pore-forming region (known as H5 or SS1-SS2). Our results suggest that the structural motif for K⁺ channels has been conserved between plants and animals.