Title: Connexins
Literature References: Family of gap-junction structural proteins found in virtually all metazoans; the assembly of which permits rapid intercellular communication by ions, second messengers and small metabolites. Named as the species of origin Cx, where x is the predicted molecular mass in kDa, e.g. rat C43. These transmembrane proteins are characterized by 2 extracellular loops, 4 hydrophobic membrane regions and a cytoplasmic loop. Oligomerization into a hexamer forms a connexon or hemichannel which interacts across the extracellular gap with a corresponding connexon to complete the intercellular channel. Description of connexon structure and composition: D. L. D. Caspar et al., J. Cell Biol. 74, 605, 629 (1977). Isolation of rat C32 via molecular cloning: D. L. Paul, ibid. 103, 123 (1986). Tissue distribution: E. C. Beyer et al., ibid. 108, 595 (1987). Review of early works on gap junction structure: P. N. T. Unwin, G. Zampighi, Nature 283, 545-549 (1980); of molecular structure and biochemical characterization: E. C. Beyer et al., J. Membr. Biol. 116, 187-194 (1990). Review of biosynthesis, function and turnover: D. W. Laird, J. Bioenerg. Biomembr. 28, 311-318 (1996); of structure/activity: C. Peracchia, X. G. Wang, Braz. J. Med. Biol. Res. 30, 577-590 (1997); of mutations in human genetic diseases: V. Krutovskikh, H. Yamasaki, Mutat. Res. 462, 197-207 (2000). Review: D. A. Goodenough et al., Annu. Rev. Biochem. 65, 475-502 (1996).
Conquinamine Convallamarogenin Convallatoxin Convicine COP

An open gap junction, composed of six identical connexin proteins. Each of these six units is a single polypeptide which passes the membrane four times (referred to as four-pass transmembrane proteins).
Symbol Connexin
Pfam PF00029
InterPro IPR013092
TCDB 1.A.24
OPM superfamily 215
OPM protein 2zw3

Connexins, or gap junction proteins, are a family of structurally related transmembrane proteins that assemble to form vertebrate gap junctions (an entirely different family of proteins, the innexins, form gap junctions in invertebrates).[1] Each gap junction is composed of two hemichannels, or connexons, which are themselves each constructed out of six connexin molecules. Gap junctions are essential for many physiological processes, such as the coordinated depolarization of cardiac muscle, proper embryonic development, and the conducted response in microvasculature. For this reason, mutations in connexin-encoding genes can lead to functional and developmental abnormalities.