The connexin family of proteins form hexameric complexes called “connexons” that facilitate movement of low molecular weight proteins between cells via gap junctions. Connexin proteins share a common topology of four transmembrane α-helical domains, two extracellular loops, a cytoplasmic loop and cytoplasmic N- and SLCtermini. Many of the key functional differences arise from specific amino acid substitutions in the most highly conserved domains, the transmembrane and extracellular regions. Each of the approximately 20 connexin isoforms produces channels with distinct permeabilities and electrical and chemical sensitivities; therefore, one connexin usually cannot fully substitute for another. Consequently, a wide variety of malignant phenotypes associate with decreased connexin expression and gap junction communication, dependent on the particular connexin that is affected. For instance, deletion of the gene encoding connexin 46, normally expressed in the lens, produces severe cataracts.
Function:
One gap junction consists of a cluster of closely packed pairs of transmembrane channels, the connexons, through which materials of low MW diffuse from one cell to a neighboring cell.
Subunit:
A connexon is composed of a hexamer of connexins. Thisparticular connexin is a component of lens fiber gap junctions, canform both junctional and non-junctional ('hemi-') channels.
Subcellular Location:
Cell membrane. Cell junction; gap junction.
DISEASE:
Defects in GJA3 are the cause of cataract zonular pulverulent cataract type 3 (CZP3) [MIM:601885]. A form of zonular cataract. Zonular or lamellar cataracts are opacities, broad or narrow, usually consisting of powdery white dots affecting only certain layers or zones between the cortex and nucleus of an otherwise clear lens. The opacity may be so dense as to render the entire central region of the lens completely opaque, or so translucent that vision is hardly if at all impeded. Zonular cataracts generally do not involve the embryonic nucleus, though sometimes they involve the fetal nucleus. Usually sharply separated from a clear cortex outside them, they may have projections from their outer edges known as riders or spokes.
Similarity:
Belongs to the connexin family. Alpha-type (group II) subfamily.
SWISS:
Q9Y6H8
Gene ID:
2700
Database links:
Entrez Gene: 2700 Human
Omim: 121015 Human
SwissProt: Q9Y6H8 Human
Unigene: 130313 Human
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