The GJB3 gene (GJB3 is the acronym for gap junction protein beta 3) is a protein-coding gene located on chromosome 1p34.3.
The gene encodes a transmembrane connexin protein that is an essential component of gap junctions.
Alternative splicing results in multiple transcript variants encoding the same protein.
Gap junctions belong to the system of cell contacts. Gap junctions (nexus, or macula communicans) consist of a collection ("plaques" or "cluster") of channels that lead through the cell membranes from cell to cell. Gap junctions thus directly connect the cytoplasm of adjacent cells. In this process, the membranes of the cells are fixed at a distance of only 2 to 4 nanometers from each other. Gap junctions, in contrast to tight junctions, leave a gap between them that can be seen under the electron microscope. The gap junction channels are formed by two hemichannels (connexons), of which each cell forms one half. Each connexon generally consists of 6 membrane-spanning proteins (in vertebrates, these are formed by the protein family of connexins - also membrane proteins). The connexins are arranged in a hexagonal pattern in such a way that a pore (gap) remains free in the middle.