title: The biotin repressor: thermodynamic coupling of corepressor binding, protein assembly, and sequence-specific DNA binding.
abstract: The Escherichia coli biotin repressor, an allosteric transcriptional regulator, is activated for binding to the biotin operator by the small molecule biotinyl-5'-AMP. Results of combined thermodynamic, kinetic, and structural studies of the protein have revealed that corepressor binding results in disorder to order transitions in the protein monomer that facilitate tighter dimerization. The enhanced stability of the dimer leads to stabilization of the resulting biotin repressor-biotin operator complex. It is not clear, however, that the allosteric response in the system is transmitted solely through the protein-protein interface. In this work, the allosteric mechanism has been quantitatively probed by measuring the biotin operator binding and dimerization properties of three biotin repressor species: the apo or unliganded form, the biotin-bound form, and the holo or bio-5'-AMP-bound form. Comparisons of the pairwise differences in the bioO binding and dimerization energetics for the apo and holo species reveal that the enhanced DNA binding energetics resulting from adenylate binding track closely with the enhanced assembly energetics. However, when the results for repressor pairs that include the biotin-bound species are compared, no such equivalence is observed.
authors.affiliation: Department of Chemistry and Biochemistry, College of Life Sciences, University of Maryland, College Park, Maryland 20742, USA.
authors.forename: Emily D
authors.initials: ED
authors.lastname: Streaker
authors.forename: Aditi
authors.initials: A
authors.lastname: Gupta
authors.forename: Dorothy
authors.initials: D
authors.lastname: Beckett
mesh_terms: D000495:Allosteric Site; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001483:Base Sequence; D001710:Biotin / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism; D019731:Carbon-Nitrogen Ligases / Q000737:chemistry / Q000378:metabolism; D018983:DNA Footprinting / Q000379:methods; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D003850:Deoxyribonuclease I; D019281:Dimerization; D004789:Enzyme Activation; D029968:Escherichia coli Proteins; D008024:Ligands; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D012097:Repressor Proteins / Q000737:chemistry* / Q000378:metabolism; D013816:Thermodynamics; D014157:Transcription Factors; D014461:Ultracentrifugation
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D008024:Ligands; D012097:Repressor Proteins; D014157:Transcription Factors; D001710:Biotin; D003850:Deoxyribonuclease I; D019731:Carbon-Nitrogen Ligases; C058125:birA protein, E coli