Structural basis for negative regulation of the Escherichia coli maltose system.

Proteins from the signal transduction ATPases with numerous domains (STAND) family are known to play an important role in innate immunity. However, it remains less well understood how they function in transcriptional regulation. MalT is a bacterial STAND that controls the Escherichia coli maltose system.

Double autoinhibition mechanism of signal transduction ATPases with numerous domains (STAND) with a tetratricopeptide repeat sensor.

Upon triggering by their inducer, signal transduction ATPases with numerous domains (STANDs), initially in monomeric resting forms, multimerize into large hubs that activate target macromolecules. This process requires conversion of the STAND conserved core (the NOD) from a closed form encasing an ADP molecule to an ATP-bound open form prone to multimerize. In the absence of inducer, autoinhibitory interactions maintain the NOD closed.

A dual role for the inducer in signalling by MalT, a signal transduction ATPase with numerous domains (STAND).

Signal transduction ATPases with numerous domains (STAND) are widespread proteins, whose activation involves inducer-dependent conversion of resting ADP-bound monomers into active ATP-bound multimers. This process notably comprises opening of the nucleotide-binding oligomerization domain (NOD), nucleotide exchange and NOD-mediated multimerization. How inducer binding to the sensor domain, whose structure is not conserved throughout the STAND family, causes protein activation remains unclear.

The ABC transporter MalFGK(2) sequesters the MalT transcription factor at the membrane in the absence of cognate substrate.

MalK, the cytoplasmic component of the maltose ABC transporter from Escherichia coli is known to control negatively the activity of MalT, the activator of the maltose regulon, through complex formation. Here we further investigate this regulatory process by monitoring MalT activity and performing fluorescence microscopy analyses under various conditions. We establish that, under physiological conditions, the molecular entity that interacts with MalT is not free MalK, but the maltose transporter, MalFGK(2) , which sequesters MalT to the membrane.

Conserved motifs involved in ATP hydrolysis by MalT, a signal transduction ATPase with numerous domains from Escherichia coli.

The signal transduction ATPases with numerous domains (STAND) are sophisticated signaling proteins that are related to AAA+ proteins and control various biological processes, including apoptosis, gene expression, and innate immunity. They function as tightly regulated switches, with the off and on positions corresponding to an ADP-bound, monomeric form and an ATP-bound, multimeric form, respectively. Protein activation is triggered by inducer binding to the sensor domain.

Wheel of Life, Wheel of Death: A Mechanistic Insight into Signaling by STAND Proteins.

The signal transduction ATPases with numerous domains (STAND) represent a newly recognized class of widespread, sophisticated ATPases that are related to the AAA+ proteins and that function as signaling hubs. These proteins control diverse biological processes in bacteria and eukaryotes, including gene expression, apoptosis, and innate immunity responses. They function as tightly regulated switches, with the off and on positions corresponding to a long-lived monomeric, ADP-bound form and a multimeric, ATP-bound form, respectively.

How integration of positive and negative regulatory signals by a STAND signaling protein depends on ATP hydrolysis.

The role of nucleotide hydrolysis in signaling by signal transduction ATPases with numerous domains (STAND) is poorly understood. Here we use MalT, the transcription activator of the Escherichia coli maltose regulon, as a model system to address this question. We have constructed the MalT-D129A variant that binds ATP but does not hydrolyze it and have characterized it in vivo and in vitro.

Two domains of MalT, the activator of the Escherichia coli maltose regulon, bear determinants essential for anti-activation by MalK.

MalT, the dedicated transcriptional activator of the maltose regulon in Escherichia coli, is subject to multiple controls. Maltotriose, the inducer, promotes MalT self-association, a critical step in promoter binding, whereas three proteins acting as negative allosteric effectors (MalK, the ABC-component of the maltodextrin transporter, MalY, and Aes) antagonize maltotriose binding. All of these regulatory signals are integrated by a novel signal transduction module that comprises three out of the four MalT structural domains: DT1, the ATP-binding domain that contains determinants recognized by the negative effectors, DT2, and DT3, the maltotriose-binding domain.

Oligomeric assemblies of the Escherichia coli MalT transcriptional activator revealed by cryo-electron microscopy and image processing.

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.

MalK, the ATP-binding cassette component of the Escherichia coli maltodextrin transporter, inhibits the transcriptional activator malt by antagonizing inducer binding.

MalK, the ATP-binding cassette component of the Escherichia coli maltodextrin transporter, has long been known to control negatively the activity of MalT, a transcriptional activator dedicated to the maltose regulon. By using a biochemical approach and the soluble form of MalK as a model substrate, we demonstrate that MalK alone inhibits transcription activation by MalT in a purified transcription system. The inhibitory effect observed in vitro is relieved by maltotriose and by two malT mutations and one malK mutation known to interfere with MalT repression by MalK in vivo.

The N terminus of the Escherichia coli transcription activator MalT is the domain of interaction with MalY.

The maltose system of Escherichia coli consists of a number of genes encoding proteins involved in the uptake and metabolism of maltose and maltodextrins. The system is positively regulated by MalT, its transcriptional activator. MalT activity is controlled by two regulatory circuits: a positive one with maltotriose as effector and a negative one involving several proteins.

The Aes protein directly controls the activity of MalT, the central transcriptional activator of the Escherichia coli maltose regulon.

MalT, the transcriptional activator of the maltose regulon from Escherichia coli, is the prototype of a new family of transcription factors. Its activity is controlled by multiple regulatory signals. ATP and maltotriose (the inducer) are two effectors of the activator that positively control its multimerization, a critical step in promoter binding.