SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) regulate activity and cell surface distribution of ion channels through direct physical interactions with the channels. I examined the structure-functional interactions between KV1.2, an important delayed rectifier K + channel in esophageal smooth muscle (ESM), and different Syntaxin1A (Syn1A) proteins. Wild type (WT) Syn1A, unlike the open form, potently inhibited KV1.2 currents and channel kinetics in the KV1.2-expressing HEK293 cells. WT and open form Syn1A and the H3-domain of Syn1A but not its HABC-domain bound ESM and tsA cell extracts' KV1.2. The inhibition of KV1.2 by WT Syn1A is not due to a defect in channel surfacing. In fact, WT Syn1A increased KV1.2 channel surfacing. Therefore, the H3-KV1.2 linkage within a closed conformation of Syn1A conveys the functional inhibition of the ESM KV1.2. This thesis provides the first evidence that the structure-function relationships are different between secretory cells and non-secretory cells such as ESM.