title: Crystallization and preliminary X-ray studies on the co-repressor binding domain of the Escherichia coli purine repressor.
abstract: The purine repressor is a putative helix-turn-helix DNA-binding protein that regulates several genetic loci important in purine and pyrimidine metabolism in Escherichia coli. The protein is composed of two domains, an N-terminal DNA-binding domain and a C-terminal core that binds the purine co-repressors, guanine and hypoxanthine. The co-repressor binding domain (residues 53 to 341) has been crystallized from polyethylene glycol 600-MgCl2 solutions. They are of the monoclinic form, space group P2(1), with a = 38.2 A, b = 125.7 A, c = 61.8 A and beta = 100.2 degrees. They diffract to a resolution of at least 2.2 A and contain two monomers per asymmetric unit. The importance of the structural determination of this domain is underscored by the high degree of sequence homology displayed within the effector binding sites among a sub-class of helix-turn-helix proteins, of which LacI and GalR are members. The structure of the PurR co-repressor binding domain will provide a high resolution view of one such domain and could serve as a possible model for future effector site structural determinations. Perhaps more important will be this structure's contribution to the further understanding of how protein-DNA interactions are modulated.
authors.affiliation: Department of Biochemistry and Molecular Biology, Oregon Health Sciences University, Portland 97201-3098.
authors.forename: M A
authors.initials: MA
authors.lastname: Schumacher
authors.forename: K Y
authors.initials: KY
authors.lastname: Choi
authors.forename: H
authors.initials: H
authors.lastname: Zalkin
authors.forename: R G
authors.initials: RG
authors.lastname: Brennan
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000737:chemistry*; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D011487:Protein Conformation; D012097:Repressor Proteins / Q000737:chemistry* / Q000378:metabolism; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C065825:PurR protein, Bacteria; C489317:PurR protein, E coli; D012097:Repressor Proteins