Gap Junctions

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Gap junctions are composed of hexagonal arrays of membranous particles that form true aqueous channels between cells. The channels, or connexons, are roughly 8 nm in diameter with a 2 nm pore. The major protein in purified preparations of gap junctions is connexin, which, when expressed in cells that normally do not have gap junctions, allows them to form. Different species of connexin are seen in different organisms and, within an organism, among tissues, but share a common structure of four membrane-spanning domains, with both carboxy and amino terminal sequences being cytoplasmic. Gap junctions allow direct intercellular traffic of small molecules and, as is often the case, large numbers of gap junctions engender ionic and metabolic coupling between cells. Aside from ions, examples of molecules that can pass through gap junctions include cyclic AMP (329 Da) , glucose-6-phosphate (259 Da), nucleotides (250-300 Da) and tetrahydrofolic acid (445 Da).

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Last updated on November 27, 1996
Comments: rbowen@vetmed.colostate.edu