Hemi-connexons

Different cells express different connexin isoforms, which make for great variations in binding affinities between different hemi-connexons. Connexons do form between cells of different types but not all heterogeneous hemi-connexon combinations support the formation of connexons between different cells. This may be... 

Figure 2. Proposed structural organization of connexin proteins into the plasma membrane to form a connexon unit. Panel A Each hemi-connexon is composed of six identical protein units arranged to circle the water filled pore, hemi-connexons dock with equivalent structures in adjacent cells to form an intact gap junction. Panel B topography of the connexin 43 protein in the plasma membrane. There are believed to be four trans-membrane spanning domains, the third of which is believed to line the water filled pore. The two extra-cellular loops are believed to dock with equivalent loops donated by connexins from the adjacent cell. (From [27] with permission).

---