Protein:Protein Interactions in Control of a Transcriptional Switch

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• 作者：Poorni R. Adikaram ; Dorothy Beckett
• 关键词：bio-5&prime ; -AMP ; biotinoyl-5&prime ; -adenylate ; bioO ; biotin operator ; BCCP ; biotin carboxyl carrier protein ; BCCP87 ; C-terminal fragment of BCCP ; holoBirA ; BirA ; biotinoyl-5&prime ; -AMP complex
• 刊名：Journal of Molecular Biology
• 出版年：15 November, 2013
• 年：2013
• 卷：425
• 期：22
• 页码：4584-4594
• 全文大小：1339 K

文摘

Protein partner exchange plays a key role in regulating many biological switches. Although widespread, the mechanisms dictating protein partner identity and, therefore, the outcome of a switch have been determined for a limited number of systems. The Escherichia coli protein BirA undergoes a switch between posttranslational biotin attachment and transcription repression in response to cellular biotin demand. Moreover, the functional switch reflects formation of alternative mutually exclusive protein:protein interactions by BirA. Previous studies provided a set of alanine-substituted BirA variants with altered kinetic and equilibrium parameters of forming these interactions. In this work, DNase I footprinting measurements were employed to investigate the consequences of these altered properties for the outcome of the BirA functional switch. The results support a mechanism in which BirA availability for DNA binding and, therefore, transcription repression is controlled by the rate of the competing protein:protein interaction. However, occupancy of the transcriptional regulatory site on DNA by BirA is exquisitely tuned by the equilibrium constant governing its homodimerization.