Human alpha-endosulfine is an endogenous regulator of the beta-cell K(ATP) channels. The recombinant alpha-endosulfine inhibits sulfonylurea binding to beta-cell membranes, reduces cloned K(ATP) channel currents, and stimulates insulin secretion from beta-cells. These properties led us to study the human ENSA gene that encodes alpha-endosulfine. Here, we describe the isolation, the partial characterization, and the chromosomal localization of the ENSA gene. The ENSA gene appears to be a 1.8-kb-long sequence that contains the transcription initiation site located 528 bp upstream of the initiation codon. The ENSA gene is intronless, and a single copy gene seems to be present in the genome. Finally, the ENSA gene co-localizes on human chromosome 14 (14q24.3-q31) with a locus for susceptibility to type 1 diabetes called IDDM11; thus, the ENSA gene represents an IDDM11 candidate.