1.A.25.1.7
Innexin-6 protein, Inx-6 or Opu-6, of 389 aas and 4 TMSs. A single INX-6 gap junction channel consists of 16 subunits, a hexadecamer, in contrast to chordate connexin channels, which consist of 12 subunits. The channel pore diameters at the cytoplasmic entrance and extracellular gap region are larger than those of connexin26 (Oshima et al. 2016). Nevertheless, the arrangements of the transmembrane helices and extracellular loops of the INX-6 monomer are highly similar to those of connexin-26 (Cx26). The INX-6 gap junction channel comprises hexadecameric subunits but reveals an N-terminal pore funnel consistent with Cx26. The helix-rich cytoplasmic loop and C-terminus are intercalated through an octameric hemichannel, forming a dome-like entrance that interacts with N-terminal loops in the pore (Oshima et al. 2016).