title: The solution structures of the trp repressor-operator DNA complex.
abstract: The solution structures of the complex between Escherichia coli trp holorepressor and a 20 base-pair consensus operator DNA were determined. The majority of proton chemical shifts of the trp holorepressor and operator DNA were assigned from homonuclear 2D NOESY spectra of selectively deuterated analog-operator DNA complexes and the 3D NOESY-HMQC spectrum of a uniformly 15N-labeled repressor-operator DNA complex. The structures were calculated using restrained molecular dynamics and sequential simulated annealing with 4086 NOE and other experimental constraints. The root-mean-squared deviation (RMSD) among the calculated structures and their mean is 0.9(+/- 0.3)A for the repressor backbone, 1.1(+/- 0.5)A for the DNA backbone, and 1.3(+/- 0.3)A for all heavy atoms. The DNA is deformed to a significant extent from the standard B DNA structure to fit the helix-turn-helix (HTH) segment of the repressor (helices D and E) into its major grooves. Little change is found in the ABCF core of the repressor on complexation in comparison to the free repressor, but changes in the cofactor L-tryptophan binding pocket and the HTH segment are observed. The N-terminal residues (2 to 17) are found to be disordered and do not form stable interactions with DNA. Direct H-bonding to the bases of the operator DNA is consistent with all of our observed NOE constraints. Hydrogen bonds from NH eta 1 and NH eta 2 of Arg69 to O-6 and N-7 of G2 are compatible with the solution structure, as they are with the crystal structure. Other direct H-bonds from Lys72, Ala80, Ile79, Thr83 and Arg84 to base-pair functional groups can also be formed in our solution structures.
authors.affiliation: Stanford Magnetic Resonance Laboratory, CA 94305-5055.
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.forename: D
authors.initials: D
authors.lastname: Zhao
authors.forename: M
authors.initials: M
authors.lastname: Revington
authors.forename: W
authors.initials: W
authors.lastname: Lee
authors.forename: X
authors.initials: X
authors.lastname: Jia
authors.forename: C
authors.initials: C
authors.lastname: Arrowsmith
authors.forename: O
authors.initials: O
authors.lastname: Jardetzky
mesh_terms: D000595:Amino Acid Sequence; D001059:Apoproteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000378:metabolism*; D029968:Escherichia coli Proteins; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009875:Operator Regions, Genetic; D009994:Osmolar Concentration; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism
chemical_list: D001059:Apoproteins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; C027190:TRPR protein, E coli; D014364:Tryptophan