title: The biotin repressor: modulation of allostery by corepressor analogs.
abstract: The Escherichia coli biotin repressor functions in biotin retention and regulation of biotin biosynthesis. Biotin retention is accomplished via the two-step biotinylation of the biotin-dependent enzyme, acetyl-CoA carboxylase. In the first step of this reaction the substrates biotin and ATP are utilized in synthesis of the activated biotin, biotinyl-5'-AMP, while in the second step this activated biotin is transferred to a unique lysine residue of the biotin carboxyl carrier protein subunit of the carboxylase. Regulation of biotin biosynthesis is accomplished through binding of the repressor to the transcription control region of the biotin biosynthetic operon. The adenylated or activated biotin functions as the corepressor in this DNA binding process. The activated biotin is a mixed anhydride and thus labile. In efforts to develop tools for structural and thermodynamic studies of the biotin regulatory interactions, two analogs of the adenylate, a sulfamoyl derivative and an ester derivative, have been synthesized and functionally characterized. Results of fluorescence measurements indicate that both analogs bind with high affinity to the repressor and that both are inactive in biotin transfer to the acceptor protein. Functional studies of their corepressor properties indicate that while the sulfamoyl is a weak allosteric activator, the ester closely mimics the physiological corepressor in activation of assembly of the transcription repression complex. Results of these studies also provide further insight into the allosteric mechanism of the biotin repressor.
authors.affiliation: Department of Chemistry and Biochemistry, College of Life Sciences, University of Maryland, College Park, MD 20472, USA.
authors.forename: Patrick H
authors.initials: PH
authors.lastname: Brown
authors.forename: John E
authors.initials: JE
authors.lastname: Cronan
authors.forename: Morten
authors.initials: M
authors.lastname: Grøtli
authors.forename: Dorothy
authors.initials: D
authors.lastname: Beckett
mesh_terms: D000249:Adenosine Monophosphate / Q000031:analogs & derivatives* / Q000378:metabolism*; D000494:Allosteric Regulation; D001483:Base Sequence; D001710:Biotin / Q000031:analogs & derivatives* / Q000378:metabolism*; D019731:Carbon-Nitrogen Ligases / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: C082099:5'-AMP-biotin; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C036824:biotin repressor; D000249:Adenosine Monophosphate; D001710:Biotin; D019731:Carbon-Nitrogen Ligases; C058125:birA protein, E coli