The similarity between the primary structures of two non-histone chromosomal proteins

A comparison has been made of two non-histone chromosomal proteins, high-mobility-group proteins 1 and 2. Peptides produced from the two proteins by various chemical and enzymic cleavages have been compared by polyacrylamide gel electrophoresis and peptide mapping. In addition the cysteine content, C-terminal sequences and amide content have been determined for both proteins. The results obtained, together with previous results, show that high-mobility-group proteins 1 and 2 have closely related primary structures, although obviously being different molecules. When analysed by isoelectric focusing both proteins exhibit complex banding patterns. In the case of high-mobility-group protein 1, this could be caused by aggregation, but with high-mobility-group protein 2 there are four distinctive subfractions focusing between pH 7.8 and 8.9.