A novel splice variant of sulfonylurea receptor 1 (SUR1), a regulatory subunit of K_ATP-channels, is described. SUR1 mRNA lacking exon 2 (SUR1D2) was discovered in human heart using a transcript scanning approach and 5'RACE-PCR. The omission of exon 2 causes a frame shift and an immediate stop codon in Exon 3 leading to a "walking stick"-like peptide composed of the N-terminal extracellular domain and the first transmembrane helix of SUR1 containing the most prominent sulfonylurea-receptor-family signature sequence. Tissue distribution experiments reveal detectable SUR1D2 in human heart and skeletal muscle, brain and spinal cord, testis and uterus, as well as pancreas. In some tissues, SUR1D2 is expressed concurrently with SUR1 and their ratio differs between individuals. Whole cell patch clamp experiments with Rin5mF cells expressing SUR1 containing K_ATP-channels show, that current is strongly increased in SUR1D2 transfected cells at 2 mM intracellular ATP. We conclude that SUR1D2 is a novel endogenous K_ATP-channel opening peptide.