title: The natural DNA bending angle in the lac repressor headpiece-O1 operator complex is determined by protein-DNA contacts and water release.
abstract: We performed molecular dynamics simulations of the lac repressor headpiece-O1 operator complex for natural, over and underbent DNA to assess the factors that determine the natural DNA bending angle. At the natural angle, the specific and nonspecific contacts between the protein and DNA are optimized. Protein-DNA contacts show different angle dependences in the right and left sites, with the left site generally getting weaker and the right site getting stronger as the bending angle increases. Two entropic factors were identified as well: at the natural bending angle, water release and the quasiharmonic protein configurational entropy are maximized. The gain in protein configurational entropy might stem from an entropy-entropy compensation mechanism, in which a reduction in protein fluctuations is offset by a loss in correlations between the right and left sites.
authors.affiliation: Department of Chemistry and Biochemistry, Center for Biological Physics, Arizona State University, PO Box 871604, Tempe, AZ 85287, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Barr
authors.forename: Arjan
authors.initials: A
authors.lastname: van der Vaart
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D019277:Entropy; D056968:Lac Repressors / Q000737:chemistry / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D014867:Water / Q000378:metabolism*
chemical_list: D056968:Lac Repressors; D014867:Water; D004247:DNA