Dimerization of the Escherichia coli Biotin Repressor: Corepressor Function in Protein Assembly

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• 作者：Edward Eisenstein and Dorothy Beckett
• 刊名：Biochemistry
• 出版年：1999
• 出版时间：October 5, 1999
• 年：1999
• 卷：38
• 期：40
• 页码：13077 - 13084
• 全文大小：95K
• 年卷期：v.38,no.40(October 5, 1999)
• ISSN：1520-4995

文摘

The repressor of biotin biosynthesis binds to the biotin operator sequence to repress transcriptioninitiation at the biotin biosynthetic operon. Site-specific binding of BirA to the biotin operator is allostericallyregulated by binding of the small molecule, biotinyl-5'-adenylate (bio-5'-AMP). The operator is a 40base pair imperfect inverted palindrome and two holorepressor monomers bind cooperatively to the twooperator half-sites. Results of previous detailed analyses of binding of holoBirA to bioO indicate thatsite-specific DNA binding and protein dimerization are obligatorily linked in the system. In the presentwork equilibrium sedimentation measurements have been used to examine the assembly properties of theaporepressor and its complexes with small ligands biotin and bio-5'-AMP. Results of these measurementsindicate that while the free protein and the biotin complex exhibit no tendency to self-associate, theadenylate-bound protein assembles into dimers with an equilibrium constant of 11 M. The results suggestthat one mechanism by which the adenylate promotes binding of BirA to the biotin operator is by promotingrepressor dimerization.