Role of the protein alpha helixes in histone-DNA interactions studied by vibrational spectroscopy.
The localization of structurally important histone-DNA interactions has been investigated by vibrational spectroscopy. Histones H2A, H2B, and H4 and their fragments (H2A, 1-56, 1-89, 73-129; H2B, 1-59, 1-83; H4, 1-53, 1-67, 1-84, 69-84, 85-102) have been prepared, characterized, and used to reconstitute protein-DNA complexes. Evidence is given for the existence of a direct relationship between the presence of ordered alpha-helical structures in the histones and a stabilization of the DNA in a B geometry. Infrared linear and ultraviolet dichroism measurements indicate that the N-terminal fragments, rich in basic residues and mostly in a random conformation, remain without any influence on the secondary structure of the nucleic acid, leaving it free in the complexes to undergo a total B----A conformational transition. On the contrary, histone fragments that involve some alpha-helical parts of the protein partially stabilize the DNA in a B geometry. Histone fragments that contain all of the alpha helixes of the protein block the DNA in the same way as the whole corresponding histone. A model for histone-DNA interactions in the core particle is discussed.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002417:Cattle; D002843:Chromatin / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D003852:Deoxyribonucleoproteins / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D010446:Peptide Fragments / Q000032:analysis; D011485:Protein Binding; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared; D013950:Thymus Gland / Q000378:metabolism; D014732:Vibration
D000596:Amino Acids; D002843:Chromatin; D003852:Deoxyribonucleoproteins; D006657:Histones; D010446:Peptide Fragments; D004247:DNA