The Biotin Repressor: Thermodynamic Coupling of Corepressor Binding, Protein Assembly, and Sequence-Specific DNA Binding

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• 作者：Emily D. Streaker ; Aditi Gupta ; and Dorothy Beckett
• 刊名：Biochemistry
• 出版年：2002
• 出版时间：December 3, 2002
• 年：2002
• 卷：41
• 期：48
• 页码：14263 - 14271
• 全文大小：236K
• 年卷期：v.41,no.48(December 3, 2002)
• ISSN：1520-4995

文摘

The Escherichia coli biotin repressor, an allosteric transcriptional regulator, is activated forbinding 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 toorder transitions in the protein monomer that facilitate tighter dimerization. The enhanced stability of thedimer 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-proteininterface. In this work, the allosteric mechanism has been quantitatively probed by measuring the biotinoperator binding and dimerization properties of three biotin repressor species: the apo or unligandedform, the biotin-bound form, and the holo or bio-5'-AMP-bound form. Comparisons of the pairwisedifferences in the bioO binding and dimerization energetics for the apo and holo species reveal that theenhanced DNA binding energetics resulting from adenylate binding track closely with the enhancedassembly energetics. However, when the results for repressor pairs that include the biotin-bound speciesare compared, no such equivalence is observed.