title: Substrate binding to DNA photolyase studied by electron paramagnetic resonance spectroscopy.
abstract: Structural changes in Escherichia coli DNA photolyase induced by binding of a (cis,syn)-cyclobutane pyrimidine dimer (CPD) are studied by continuous-wave electron paramagnetic resonance and electron-nuclear double resonance spectroscopies, using the flavin adenine dinucleotide (FAD) cofactor in its neutral radical form as a naturally occurring electron spin probe. The electron paramagnetic resonance/electron-nuclear double resonance spectral changes are consistent with a large distance (> or =0.6 nm) between the CPD lesion and the 7,8-dimethyl isoalloxazine ring of FAD, as was predicted by recent model calculations on photolyase enzyme-substrate complexes. Small shifts of the isotropic proton hyperfine coupling constants within the FAD's isoalloxazine moiety can be understood in terms of the cofactor binding site becoming more nonpolar because of the displacement of water molecules upon CPD docking to the enzyme. Molecular orbital calculations of hyperfine couplings using density functional theory, in conjunction with an isodensity polarized continuum model, are presented to rationalize these shifts in terms of the changed polarity of the medium surrounding the FAD cofactor.
authors.affiliation: Institute of Experimental Physics, Free University Berlin, 14195 Berlin, Germany. stefan.weber@physik.fu-berlin.de
authors.forename: S
authors.initials: S
authors.lastname: Weber
authors.forename: G
authors.initials: G
authors.lastname: Richter
authors.forename: E
authors.initials: E
authors.lastname: Schleicher
authors.forename: A
authors.initials: A
authors.lastname: Bacher
authors.forename: K
authors.initials: K
authors.lastname: Möbius
authors.forename: C W
authors.initials: CW
authors.lastname: Kay
mesh_terms: D001665:Binding Sites; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000737:chemistry* / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000201:enzymology*; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D011485:Protein Binding; D011522:Protons; D011740:Pyrimidine Dimers / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D011522:Protons; D011740:Pyrimidine Dimers; D005182:Flavin-Adenine Dinucleotide; D004255:Deoxyribodipyrimidine Photo-Lyase