title: Effect of pH on interactions between DNA and high-mobility group protein HMG1.
abstract: Fluorescence quenching was used to test the effect of pH changes on the binding of high-mobility group protein 1 (HMG1) to double-stranded and single-stranded DNA. At pH 7.5, the binding constant K for double-stranded DNA was 3 x 10(6) M-1, the binding site size n was 13, and the cooperativity factor q was 78, while at pH 6 the corresponding values were K = 12 x 10(6) M-1, n = 54, and q = 770. For the binding of HMG1 to single-stranded DNA at pH 7.5, the values were K = 2 x 10(6) M-1, n = 7, and q = 60, whereas at pH 6 they were K = 3 x 10(6) M-1, n = 14, and q = 440. Denaturation of HMG1 by oxidation of its sulfhydryl groups substantially affected the binding parameters. At pH 6, double-stranded DNA bound oxidized HMG1 with K = 6 x 10(6) M-1, n = 16, and q = 200, and single-stranded DNA bound with K = 3 x 10(6) M-1, n = 7, and q = 180. The sensitivity of the double-stranded DNA-HMG1 interaction to pH, along with an earlier report of a sharp optimum of binding at 140 mM NaCl, reveals a potential for in vivo regulation of the strength and mode of HMG1 binding by DNA through the action of analogous factors in the cellular milieu.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley 94720.
authors.forename: L A
authors.initials: LA
authors.lastname: Kohlstaedt
authors.forename: R D
authors.initials: RD
authors.lastname: Cole
mesh_terms: D004247:DNA / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism; D006609:High Mobility Group Proteins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D011485:Protein Binding / Q000502:physiology; D011489:Protein Denaturation / Q000502:physiology; D013050:Spectrometry, Fluorescence
chemical_list: D004277:DNA, Single-Stranded; D006609:High Mobility Group Proteins; D004247:DNA