Calcium-activated chloride channels (CaCC) are present in many cell types and mediate physiological functions such as epithelial secretion, sensory signal transduction, and smooth muscle contraction. Subunits of these CaCCs include the transmembrane proteins TMEM16A and TMEM16B. TMEM16B is predicted to have eight transmembrane domains with both the amino and carboxy termini in the cytoplasm and is expressed in several tissues including olfactory sensory neurons as well as photoreceptors in mammalian retina. Like TMEM16A, TMEM16B is thought to form at least part of CaCC's but has different biophysical characteristics such as voltage dependence and unitary conductance.