Specific amino-acid residues in the N-terminus and TM3 implicated in channel function and oligomerization compatibility of connexin43.

To identify signals that convey connexin oligomerization compatibility, we have aligned amino-acid sequences of alpha and beta group connexins (Cx) and compared the physico-chemical properties of each homologous amino-acid residue. Four positions were identified that consistently differed between alpha and beta-type connexins; two are located in the N-terminal domain (P1 and P2, corresponding to residues 12 and 13 of the Cx43 sequence), and two in the third trans-membrane-spanning domain TM3 (P3 and P4, corresponding to residues 152 and 153 of the Cx43 sequence). Replacement of each of these residues in Cx43 (an alpha-type connexin) with the corresponding residues of Cx32 (a beta-type connexin) resulted in the assembly of all variants into gap junctions; however, only the P4 variant was functional, as indicated by lucifer yellow dye transfer assays.