Biochemical and immunological approaches to the study of gap junctional communication

Studies on gap junctions isolated from rat liver by a procedure that avoids exogenous proteolysis (Hertzberg, E. L.; Gilula. N. B.; J. Biol. Chem. 254: 2138-2147; 1979) are described. The original isolation procedure was modified to increase the yield and has been extended to the preparation of gap junctions from mouse and bovine liver. Peptide map studies showed that the 27,000-dalton polypeptides present in liver gap junction preparations from all three sources are homologous and are not derived from other polypeptides of higher molecular weight that are observed in cruder preparations. Similar studies with lens fiber junctions demonstrated no homology between liver and lens junction polypeptides. Antibodies to the lens junction polypeptides did not cross-react with the liver gap junction polypeptide, further supporting this conclusion.