The dissociation of nuclear proteins from superhelical DNA.
Structures retaining many of the morphological features of nuclei may be released by gently lysing human cells in solutions containing non-ionic detergents and high concentrations of salt. These nucleoids contain superhelical DNA. Using a double-labelling procedure we have compared, at different salt concentrations, the amounts and types of protein associated with human nucleoides containings superhelical or relaxed DNA. We find that the slightly lysine-rich histones (H2A and H2B) but not the arginine-rich histones (H3 and H4) dissociate more slowly from nucleoids containing superhelical DNA than from those containing relaxed DNA. A protein of apparent molecular weight of 22000 also binds more tightly to superhelical DNA. We conclude that this protein and the slightly lysine-rich histones transmute free energy of supercoiling into binding energy when they bind to superhelical DNA.
D001120:Arginine / Q000378:metabolism; D004278:DNA, Superhelical; D006657:Histones / Q000378:metabolism; D007700:Kinetics; D008239:Lysine / Q000378:metabolism; D008970:Molecular Weight; D009690:Nucleic Acid Conformation; D009698:Nucleoproteins; D011485:Protein Binding
D004278:DNA, Superhelical; D006657:Histones; D009698:Nucleoproteins; D001120:Arginine; D008239:Lysine