Cx23, a connexin with only four extracellular-loop cysteines, forms functional gap junction channels and hemichannels.
Gap junction channels may be comprised of either connexin or pannexin proteins (innexins and pannexins). Membrane topologies of both families are similar, but sequence similarity is lacking. Recently, connexin-like sequences have been identified in mammalian and zebrafish genomes that have only four conserved cysteines in the extracellular domains (Cx23), a feature of the pannexins. Phylogenetic analyses of the non-canonical "C4" connexins reveal that these sequences are indeed connexins. Functional assays reveal that the Cx23 gap junctions are capable of sharing neurobiotin, and further, that Cx23 connexins form hemichannels in vitro.
Iovine
M Kathryn
MK
Department of Biological Sciences, Lehigh University, 111 Research Drive, Bethlehem, PA 18015, USA. mki3@lehigh.edu
Gumpert
Anna M
AM
Falk
Matthias M
MM
Mendelson
Tamra C
TC
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017630:Connexins / Q000737:chemistry / Q000502:physiology*; D003545:Cysteine / Q000737:chemistry*; D017931:DNA Primers; D017629:Gap Junctions / Q000737:chemistry / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D017403:In Situ Hybridization; D007908:Lens, Crystalline / Q000378:metabolism; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D015027:Zebrafish
D017630:Connexins; D017931:DNA Primers; D003545:Cysteine