1. Structural comparison of the free and DNA-bound forms of the purine repressor DNA-binding domain
- Author
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Souichi Morikawa, G. Sampei, K. Kobayashi, Yoshifumi Nishimura, H. Yamamoto, Richard G. Brennan, Aritaka Nagadoi, Maria A. Schumacher, Masato Enari, Haruki Nakamura, and K. Mizobuchi
- Subjects
DNA, Bacterial ,Models, Molecular ,Magnetic Resonance Spectroscopy ,Operator Regions, Genetic ,Macromolecular Substances ,Protein Conformation ,Molecular Sequence Data ,Repressor ,DNA-induced α helix ,Helix-turn-helix ,Lac repressor ,Biology ,Protein structure ,Bacterial Proteins ,Structural Biology ,Escherichia coli ,Amino Acid Sequence ,Ternary complex ,Molecular Biology ,Helix-Turn-Helix Motifs ,Purr ,Binding Sites ,Base Sequence ,Escherichia coli Proteins ,purine repressor ,DNA-binding domain ,NMR ,Protein tertiary structure ,lactose repressor ,Repressor Proteins ,Crystallography ,Nucleic Acid Conformation ,Protein Binding - Abstract
Background: The purine repressor (PurR) regulates genes that encode enzymes for purine biosynthesis. PurR has a two domain structure with an N-terminal DNA-binding domain (DBD) and a C-terminal corepressor-binding domain (CBD). The three-dimensional structure of a ternary complex of PurR bound to both corepressor and a specific DNA sequence has recently been determined by X-ray crystallography. Results We have determined the solution structure of the PurR DBD by NMR. It contains three helices, with the first and second helices forming a helix-turn-helix motif. The tertiary structure of the three helices is very similar to that of the corresponding region in the ternary complex. The structure of the hinge helical region, however, which makes specific base contacts in the minor groove of DNA, is disordered in the DNA-free form. Conclusion The stable formation of PurR hinge helices requires PurR dimerization, which brings the hinge regions proximal to each other. The dimerization of the hinge helices is likely to be controled by the CBD dimerization interface, but is induced by specific-DNA binding.
- Published
- 1995