PMID:15491603

Citation	Larquet, E, Schreiber, V, Boisset, N and Richet, E (2004) Oligomeric assemblies of the Escherichia coli MalT transcriptional activator revealed by cryo-electron microscopy and image processing. J. Mol. Biol. 343:1159-69
Abstract	MalT, the dedicated transcriptional activator of the maltose regulon in Escherichia coli, is the prototype for a family of large (approximately 100 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.
Links	PubMed Online version:10.1016/j.jmb.2004.09.010
Keywords	Cryoelectron Microscopy; DNA-Binding Proteins/chemistry; DNA-Binding Proteins/metabolism; DNA-Binding Proteins/ultrastructure; Escherichia coli/metabolism; Escherichia coli Proteins/chemistry; Escherichia coli Proteins/metabolism; Escherichia coli Proteins/ultrastructure; Multivariate Analysis; Nucleoproteins/chemistry; Nucleoproteins/metabolism; Nucleoproteins/ultrastructure; Promoter Regions, Genetic; Transcription Factors/chemistry; Transcription Factors/metabolism; Transcription Factors/ultrastructure
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