GcvR interacts with GcvA to inhibit activation of the Escherichia coli glycine cleavage operon

Abstract

The Escherichia coli glycine cleavage enzyme system, encoded by the gcvTHP operon, catalyses the oxidative cleavage of glycine to CO 2 , NH 3 and a onecarbon methylene group. Transcription of the gcv operon is positively regulated by GcvA and negatively regulated by GcvA and GcvR. Using a LexAbased system for analysing protein heterodimerization, it is shown that GcvR interacts directly with GcvA in vivo to repress gcvTHP expression. Several mutations in either gcvA or gcvR that result in a loss of gcv repression also result in a loss of GcvA/GcvR heterodimerization. Finally, it is shown that the C-terminal half of GcvA is involved in its interaction with GcvR, whilst the entire GcvR protein appears to be necessary for heterodimerization.

Molecular Basis of Transcriptional Antiactivation

“…In the cases of NifA-NifL and ComKMecA, the antiactivator binds to and titrates the activator, thus preventing DNA binding and transcriptional activation (33)(34)(35). However in the cases of GcvA-GcvR and CRP-CytR, the antiactivator and the activator bind promoter DNA in tandem, and the interactions between the antiactivator and the activator at the promoter inhibit transcriptional activation (36,37). In this regard, the mechanism of antiactivation by TraM resembles that of NifA-NifL and ComK-MecA.…”

“…Inhibition of Ti plasmid conjugative transfer by TraM joins a growing list of prokaryotic regulatory systems involving an activator-antiactivator complex, including NifA-NifL regulation of nitrogen fixation in Azotobacter vinelandii (33) and Klebsiella pneumoniae (34), ComK-MecA-ClpC regulation of competence in Bacillus subtilis (35), GcvA-GcvR regulation of oxidative cleavage of glycine (36), and CRP-CytR regulation of many operons in E. coli (37). In the cases of NifA-NifL and ComKMecA, the antiactivator binds to and titrates the activator, thus preventing DNA binding and transcriptional activation (33)(34)(35).…”

Crystal Structure of the YgfZ Protein from Escherichia coli Suggests a Folate-Dependent Regulatory Role in One-Carbon Metabolism

“…It is tempting to speculate that YgfZ may act as a transcriptional regulator. One such uncharacterized protein has recently been shown to recognize a conserved CATCN 7 CTTCTT motif present in the promoter regions of the yeast gcv genes (10). The formation of the complex is responsive to THF, indicating that glycine-specific control may be mediated via folate derivatives.…”

“…Together, these proteins modulate transcription of the operon in response to the levels of glycine and purines. The repressor capability of GcvR is realized through complex formation with GcvA, whereas the other proteins bind directly to the gcv control region (7). Closely related to the GCS is the glycine betaine pathway that involves three demethylation steps catalyzed consecutively by betaine-homocysteine methyltransferase, dimethylglycine dehydrogenase (oxidase) (DMGO), and sarcosine dehydrogenase (oxidase) to produce glycine and C1 units (16).…”

CbbR, the Master Regulator for Microbial Carbon Dioxide Fixation

“…There are several studies that show LTTR interactions with RNA polymerase or sigma factors (50)(51)(52)(53)(54)(55), but there are few examples of interactions of LTTR proteins (not including CbbRs) with other transcriptional regulators (56,57). By and large, this is a testament to the ability of LTTRs to independently and adequately regulate their operons in the prokaryotic kingdom.…”