Dual role of CcpC protein in regulation of aconitase gene expression in Listeria monocytogenes and Bacillus subtilis

Mittal, Meghna; Pechter, Kieran B.; Picossi, Silvia; Kim, Hyun‐Jin; Kerstein, Kathryn O.; Sonenshein, Abraham L.

doi:10.1099/mic.0.063388-0

Cited by 18 publications

(23 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…If the intracellular citrate level becomes excessive, iron will be sequestered away from iron-containing proteins, including aconitase. Since excess citrate greatly stimulates aconitase synthesis via the positive regulatory effect of CcpC (11), the cell will gain the ability to metabolize citrate at a higher rate. If so much iron has been sequestered that aconitase loses enzymatic activity, the cell will acquire a high concentration of enzymatically inactive but RNA-binding-competent aconitase molecules.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Two Roles for Aconitase in the Regulation of Tricarboxylic Acid Branch Gene Expression in Bacillus subtilis

et al. 2013

Self Cite

View full text Add to dashboard Cite

cPreviously, it was shown that an aconitase (citB) null mutation results in a vast overaccumulation of citrate in the culture fluid of growing Bacillus subtilis cells, a phenotype that causes secondary effects, including the hyperexpression of the citB promoter. B. subtilis aconitase is a bifunctional protein; to determine if either or both activities of aconitase were responsible for this phenotype, two strains producing different mutant forms of aconitase were constructed, one designed to be enzymatically inactive (C450S [citB2]) and the other designed to be defective in RNA binding (R741E [citB7]). The citB2 mutant was a glutamate auxotroph and accumulated citrate, while the citB7 mutant was a glutamate prototroph. Unexpectedly, the citB7 strain also accumulated citrate. Both mutant strains exhibited overexpression of the citB promoter and accumulated high levels of aconitase protein. These strains and the citB null mutant also exhibited increased levels of citrate synthase protein and enzyme activity in cell extracts, and the major citrate synthase (citZ) transcript was present at higher-than-normal levels in the citB null mutant, due at least in part to a >3-fold increase in the stability of the citZ transcript compared to the wild type. Purified B. subtilis aconitase bound to the citZ 5= leader RNA in vitro, but the mutant proteins did not. Together, these data suggest that wild-type aconitase binds to and destabilizes the citZ transcript in order to maintain proper cell homeostasis by preventing the overaccumulation of citrate. Elimination of any one of the three enzymes of the tricarboxylic acid (TCA) branch of the Krebs cycle-citrate synthase (CS), aconitase (Acn), and isocitrate dehydrogenase-results in glutamate auxotrophy and a significant defect in spore formation in Bacillus subtilis (1-4). In particular, a null mutation in the aconitase (citB) gene causes a dramatic increase in the concentration of citrate in the culture fluid of growing cells (1). This accumulation of citrate prevents sporulation due to chelation by citrate of divalent cations required for proper functioning of the Spo0A-initiated phosphorelay (1, 4).We had assumed that citB null cells accumulate citrate simply because of the lack of aconitase enzyme activity present in this strain. As B. subtilis lacks a citrate lyase enzyme, citB null cells have no way of enzymatically removing the citrate once it is formed; thus, the citrate accumulation phenotype has been attributed solely to this metabolic roadblock. However, in this report, we present data suggesting that the actual mechanism is more complex.B. subtilis expresses one aconitase and two citrate synthase enzymes (3, 5). Aconitase is encoded by the citB gene in a single-gene transcription unit (5). The gene for the major citrate synthase, citZ, is the first gene in an operon that also includes the genes for isocitrate dehydrogenase (icd or citC) and malate dehydrogenase (mdh or citH). The gene for the minor citrate synthase, citA, is present at a separate locus and is expressed...

show abstract

Section: Discussionmentioning

confidence: 99%

“…When citrate is present, it causes a change in the interaction of CcpC with its binding sites, resulting in derepression of citB and citZ. When citrate is very abundant, CcpC activates citB expression, presumably reflecting a change in the interaction of CcpC with RNA polymerase (11).…”

mentioning

confidence: 99%

Two Roles for Aconitase in the Regulation of Tricarboxylic Acid Branch Gene Expression in Bacillus subtilis

et al. 2013

Self Cite

View full text Add to dashboard Cite

show abstract

“…None of these repressors is fully effective by itself; therefore, complete repression requires high intracellular pools of FBP, BCAAs, and GTP and low citrate, the effector of CcpC. (When citrate accumulates to high level, CcpC is inactivated as a repressor of citrate synthase and isocitrate dehydrogenase but switches from a repressor to an activator of the aconitase gene (196)). A similar regulatory scheme is found in L. monocytogenes (196).…”

Section: Metabolite-responsive Global Regulators That Influence Virulmentioning

confidence: 99%

Regulating the Intersection of Metabolism and Pathogenesis in Gram-positive Bacteria

2015

View full text Add to dashboard Cite

Pathogenic bacteria must contend with immune systems that actively restrict the availability of nutrients and cofactors, and create a hostile growth environment. To deal with these hostile environments, pathogenic bacteria have evolved or acquired virulence determinants that aid in the acquisition of nutrients. This connection between pathogenesis and nutrition may explain why regulators of metabolism in nonpathogenic bacteria are used by pathogenic bacteria to regulate both metabolism and virulence. Such coordinated regulation is presumably advantageous because it conserves carbon and energy by aligning synthesis of virulence determinants with the nutritional environment. In Gram-positive bacterial pathogens, at least three metabolite-responsive global regulators, CcpA, CodY, and Rex, have been shown to coordinate the expression of metabolism and virulence genes. In this chapter, we discuss how environmental challenges alter metabolism, the regulators that respond to this altered metabolism, and how these regulators influence the host-pathogen interaction.

show abstract

“…However, the amino acid sequence and DNA-binding sites of CcpE (Fig. 1B) are similar to those of CcpC, a citrate-responsive regulator in B. subtilis (28,29). In addition, deletion of ccpE causes a dramatic reduction of citB expression, resulting in the accumulation of citrate (23).…”

Section: Deletion Of Ccpe Led To Enhanced Staphyloxanthin Productionmentioning

confidence: 99%

“…In addition, a certain degree of protection also was seen in the region between protected regions I and II. We noted that protected region I contains a box I-like sequence (ATAA-N 7 -TTAT, where N is any nucleotide) and that protected region II contains a box II-like sequence (AATA or TTAT), as found in the binding sites of CcpC (28), a citrate-responsive regulator in Bacillus subtilis showing 61% similarity and 35% identity to CcpE (28,29).…”

Section: Deletion Of Ccpe Led To Enhanced Staphyloxanthin Productionmentioning

confidence: 99%

Metabolic sensor governing bacterial virulence in Staphylococcus aureus

Ding¹,

Liu

Chen³

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

An effective metabolism is essential to all living organisms, including the important human pathogen Staphylococcus aureus. To establish successful infection, S. aureus must scavenge nutrients and coordinate its metabolism for proliferation. Meanwhile, it also must produce an array of virulence factors to interfere with host defenses. However, the ways in which S. aureus ties its metabolic state to its virulence regulation remain largely unknown. Here we show that citrate, the first intermediate of the tricarboxylic acid (TCA) cycle, binds to and activates the catabolite control protein E (CcpE) of S. aureus. Using structural and site-directed mutagenesis studies, we demonstrate that two arginine residues (Arg145 and Arg256) within the putative inducer-binding cavity of CcpE are important for its allosteric activation by citrate. Microarray analysis reveals that CcpE tunes the expression of 126 genes that comprise about 4.7% of the S. aureus genome. Intriguingly, although CcpE is a major positive regulator of the TCA-cycle activity, its regulon consists predominantly of genes involved in the pathogenesis of S. aureus. Moreover, inactivation of CcpE results in increased staphyloxanthin production, improved ability to acquire iron, increased resistance to whole-blood-mediated killing, and enhanced bacterial virulence in a mouse model of systemic infection. This study reveals CcpE as an important metabolic sensor that allows S. aureus to sense and adjust its metabolic state and subsequently to coordinate the expression of virulence factors and bacterial virulence.Staphylococcus aureus | metabolism | iron acquisition | virulence gene expression | bacterial virulence

show abstract

Dual role of CcpC protein in regulation of aconitase gene expression in Listeria monocytogenes and Bacillus subtilis

Cited by 18 publications

References 31 publications

Two Roles for Aconitase in the Regulation of Tricarboxylic Acid Branch Gene Expression in Bacillus subtilis

Two Roles for Aconitase in the Regulation of Tricarboxylic Acid Branch Gene Expression in Bacillus subtilis

Regulating the Intersection of Metabolism and Pathogenesis in Gram-positive Bacteria

Metabolic sensor governing bacterial virulence in Staphylococcus aureus

Contact Info

Product

Resources

About