Molecular cloning of two guinea pig liver gap junction proteins, connexin32 and connexin26.

Intercellular coupling of hepatocytes through gap junctions facilitates exchange of small metabolites or ions, and contributes to maintenance of tissue homeostasis. As protein constituents of the liver gap junction channels, connexin32 (Cx32) and Cx26 have been identified. By use of rat cDNA probes, we cloned cDNAs for guinea pig homologs of Cx32 and Cx26, and compared their amino acid sequences with those of other species. The deduced primary structure of guinea pig Cx32 was 283 amino acids long and contained 98% identical amino acids to the rat and human Cx32. Only six amino acid exchanges were detected between the guinea pig and rat Cx32. On the contrary, the deduced amino acid sequence of guinea pig Cx26 (226 amino acids long) was 91 and 89% identical to the rat and human Cx26, respectively. Twenty-one amino acid exchanges were found between the guinea pig and rat, and the divergence was mostly located in cytoplasmic domains of Cx26. These results suggest that Cx26 shows structural diversity between species, while Cx32 is highly conserved.