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Binding of histone H1 to DNA is described by an allosteric model
Author(s) -
Mamoon Naila M.,
Song Yuguang,
Wellman Susan E.
Publication year - 2005
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.20172
Subject(s) - allosteric regulation , chemistry , cooperativity , cooperative binding , dna , histone , stereochemistry , conformational change , binding site , crystallography , linker , biophysics , biochemistry , enzyme , biology , computer science , operating system
Abstract Equilibrium binding data were analyzed to characterize the interaction of the linker histone H1° with unmodified T4 phage DNA. Data were cast into the Scatchard‐type plot described by McGhee and von Hippel and fit to their eponymous model for nonspecific binding of ligand to DNA. The data were not fit by the simple McGhee–von Hippel model, nor fit satisfactorily by the inclusion of a cooperativity parameter. Instead, the interaction appeared to be well described by Crothers' allosteric model, in which the higher affinity of the protein for one conformational form of the DNA drives an allosteric transition of the DNA to the conformational form with higher affinity (form 2). At 214 m M Na + , the observed affinity K for an isolated site on unmodified T4 bacteriophage DNA in the form 2 conformation is 4.5 × 10 7 M −1 . The binding constant for an isolated site on DNA in the conformation with lower affinity, form 1, appears to be about 10‐fold lower. Binding affinity is dependent on ion concentration: the magnitude of K is about 10‐fold higher at 14 m M (5.9 × 10 8 M −1 for form 2 DNA) than at 214 m M Na + concentration. © 2004 Wiley Periodicals, Inc. Biopolymers, 2005