Conformation and domain structure of the non-histone chromosomal proteins, HMG 1 and 2. Isolation of two folded fragments from HMG 1 and 2.
Proteins HMG 1 and 2 have been digested with trypsin and two major products, stable to further digestion between 8 min and 2 h, have been purified (peptides A and B). Peptide B from HMG 1 has been identified as residues 12-75 and peptide A as residues 94/96-169 by amino acid analyses and Edman degradations. Peptide B spontaneously folds with the formation of 51% helix and exhibits the majority of the perturbed NMR resonances characteristic of folded intact HMG 1. Peptide B is stably folded in the presence of 150 mM NaCl between pH 3 and 10, like intact HMG 1. Peptide A forms 30% alpha-helix and also exhibits tertiary folding but is denatured by pH 10. The 11 N-terminal residues removed by trypsin contain both sites of post-synthetic acetylation (residues 2 and 11), a situation very similar to that found with core histones. It is proposed that HMG 1 and 2 consist of four structural domains, viz: (a) residues 1-11, (b) residues 12 to approximately 75, (c) residues 94-169 and (d) the very acidic region beyond residue 169. The instability of peptide A may mean that it is not a truly independent domain. No structural similarities to histone H1 are therefore observed in HMG 1 and 2.
D000818:Animals; D002417:Cattle; D002467:Cell Nucleus / Q000032:analysis; D055598:Chemical Phenomena; D002621:Chemistry; D002868:Chromosomal Proteins, Non-Histone / Q000302:isolation & purification*; D002942:Circular Dichroism; D006609:High Mobility Group Proteins; D009682:Magnetic Resonance Spectroscopy; D010446:Peptide Fragments / Q000302:isolation & purification*; D011487:Protein Conformation; D013950:Thymus Gland / Q000032:analysis
D002868:Chromosomal Proteins, Non-Histone; D006609:High Mobility Group Proteins; D010446:Peptide Fragments