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Oligomeric Assemblies of the Escherichia coli MalT Transcriptional Activator Revealed by Cryo-electron Microscopy and Image Processing.

Abstract : MalT, the dedicated transcriptional activator of the maltose regulon in Escherichia coli, is the prototype for a family of large (not, vert, similar100 kDa) transcriptional activators. MalT self-association plays a key role in recognition of the target promoters, which contain several MalT sites that are cooperatively bound by the activator. The unliganded form of MalT is monomeric. The protein self-associates only in the presence of both ATP (or AMP-PNP, a non-hydrolysable analog of ATP) and maltotriose, the inducer. Here, we report cryo-electron microscopy analyses of MalT multimeric forms. We show that, in the presence of maltotriose and AMP-PNP, MalT associates into novel, polydisperse, curved homopolymers. The building block, corresponding to a MalT monomer, comprises an outer globular domain connected by a peduncle to an inner domain that mediates self-association. Image analyses highlight the significant conformational flexibility of these polymeric forms. In the presence of a DNA fragment containing a MalT-controlled promoter, malPp500, MalT forms homopolymers with a much smaller radius of curvature and a different conformation. We propose that MalT binding to the target promoters involves the assembly of a MalT homo-oligomer that is governed by the array of MalT sites present.
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https://hal.archives-ouvertes.fr/hal-00086710
Contributor : Sylvia Deplanque <>
Submitted on : Wednesday, July 19, 2006 - 2:45:54 PM
Last modification on : Thursday, November 19, 2020 - 8:50:29 AM

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Eric Larquet, Valérie Schreiber, Nicolas Boisset, Evelyne Richet. Oligomeric Assemblies of the Escherichia coli MalT Transcriptional Activator Revealed by Cryo-electron Microscopy and Image Processing.. Journal of Molecular Biology, Elsevier, 2004, 343, pp.1159-1169. ⟨10.1016/j.jmb.2004.09.010⟩. ⟨hal-00086710⟩

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