J Biol Chem 2002 Jul 31

pH-dependent intramolecular binding and structure involving Cx43 cytoplasmic domains

Duffy HS, Sorgen PL, Girvin ME, O'Donnell P, Coombs W, Taffet SM, Delmar M, Spray DC.

pH-induced closure of Connexin43 (Cx43) channels involves interaction of the Cx43 carboxyl terminal (Cx43CT) with a separate "receptor" domain. The receptor location and structure and whether the interaction is directly intramolecular are unknown. Here we show surface plasmon resonance and nuclear magnetic resonance (NMR) experiments demonstrating pH-dependent binding of Cx43CT to region 119-144 of Cx43 (Cx43L2), which we propose is the receptor. NMR showed pH-induced modification in Cx43CT structure and alpha-helical order in Cx43L2. These data are the first demonstration of chemically induced structural order and binding between cytoplasmic connexin domains.