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Gap junction channels, also known as connexons, are protein complexes that form gap junctions, which are specialized cell-cell junctions that allow for the direct transfer of ions, small molecules, and electrical signals between adjacent cells. These channels are composed of six connexin proteins, which are encoded by a family of genes. The connexin proteins assemble into hexamers, which then aggregate to form the connexon. Gap junction channels are found in various tissues and organs, including the heart, brain, liver, and muscle, and play crucial roles in coordinating cellular activities, maintaining tissue homeostasis, and facilitating intercellular communication.

The structure of gap junction channels is highly conserved across different species, reflecting their essential role in various biological processes. The channels are highly selective, allowing the passage of molecules up to a certain size, typically less than 1.2 nanometers in diameter. This selectivity is determined by the size and charge of the molecules, as well as the specific amino acid sequence of the connexin proteins.

Gap junction channels are regulated by various factors, including intracellular calcium levels, phosphorylation, and the expression of different connexin isoforms. Dysfunction or dysregulation of gap junction channels has been implicated in several diseases, such as cardiac arrhythmias, neurodegenerative disorders, and cancer. Therefore, understanding the molecular mechanisms underlying gap junction channel function and regulation is of great importance for developing therapeutic strategies for these diseases.