DNA and histone H1 interact with different domains of HMG 1 and 2 proteins.

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Abstract
High mobility group (HMG) proteins 1 and 2 from calf thymus have been digested under structuring conditions (0.35 M NaCl, pH 7.1) with two proteases of different specificities, trypsin and V8. The two proteases give a different but restricted pattern of peptides in a time course digestion study. However, when the interactions of the peptides with DNA are studied by blotting, a closely related peptide from HMG‐1 and ‐2 does not show any apparent binding. This peptide, from the V8 protease digestion, has been isolated by DNA‐cellulose chromatography and has the amino acid composition predicted for a fragment containing the two C‐terminal domains of the protein, i.e., approximately residues 74‐243 for HMG‐1. The same peptide shows the only interaction detectable with labelled histone H1. A separate function for the different domains of HMG proteins 1 and 2 is proposed.