Rat liver gap junction protein: properties and partial sequence.

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Abstract
Gap junctions, strongly implicated as channels for direct cell-to-cell communication, were isolated from rat liver in high yield and purity. These gap junction fractions contain few morphologically recognizable contaminants but sodium dodecyl sulfate/polyacrylamide gel electrophoresis reveals a number of polypeptides. With the exception of a nonjunctional component of MW 38,000 and some poorly soluble material, including collagen, all the polypeptides have very similar or identical 2-dimensional peptide maps and arise from proteolytic cleavage of the COOH-terminus or aggregation of a MW 28,000 protein. The sequence of the NH2-terminal 52 amino acids of this protein is reported. The polypeptide (MW .apprxeq. 10,000) characteristic of trypsin-treated gap junction preparations is shown to be 2 distinct polypeptides, both derived from the MW 28,000 protein.