This Gap 26 peptide is derived from the first extracellular loop sequence of connexin (Cx) 43. This short mimetic peptide reversibly inhibits the gap junction-dependent propagation of Ca2+ waves between tracheal airway epithelial cells. Connexins, or gap junctions, are a family of structurally-related transmembrane proteins. Gap junctions contain channels that allow the passage of ions and small molecules between adjacent cells molecules. Calcium and inositol phosphates are among the second messengers that can pass through gap junction channels.