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PubMed · 11069917

Strengthened arm-dimerization domain interactions in AraC.

M Wu·R Schleif
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Abstract

Constitutive mutations were sought and found in the N-terminal arm of the Escherichia coli regulatory protein of the arabinose operon, AraC protein. A new mutation, N16D, was of particular interest. Asn-16 is not seen in the crystal structure of the AraC dimerization domain determined in the absence of arabinose, because the N-terminal arm 18 residues are disordered, but in the presence of arabinose, residues 7-18 fold over the arabinose and make many interactions with it. In this state Asn-16 lies near two positively charged amino acids, Lys-43 and Arg-99. We propose that the introduction of the negatively charged aspartic residue at position 16 creates a charge-charge interaction network among Asp-16, Lys-43, and Arg-99 that holds the arm to the dimerization domain even in the absence of arabinose. This frees the DNA-binding domains and allows them to bind cis to I(1)-I(2) half-sites and activate transcription. Mutating the two positively charged residues to alanines individually and collectively decreased or eliminated the constitutivity created by the N16D mutation.

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AraC Transcription FactorArabinoseArginineAspartic AcidBacterial ProteinsDimerizationEscherichia coli ProteinsGene Expression Regulation, BacterialLysineModels, GeneticMutationRepressor ProteinsTranscription FactorsJournal ArticleResearch Support, U.S. Gov't, P.H.S.

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M Wu, R Schleif. 2000-11-07. Strengthened arm-dimerization domain interactions in AraC.. https://doi.org/10.1074/jbc.m008705200

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