Chlamydia trachomatis YtgA is an iron-binding periplasmic protein induced by iron restriction

Miller, Jeffrey D.; Sal, Melanie; Schell, Maria; Whittimore, Judy D.; Raulston, Jane E.

doi:10.1099/mic.0.030247-0

Cited by 27 publications

(36 citation statements)

References 41 publications

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“…Tao . The apparent preference of YtgR for iron, instead of zinc is consistent with iron-related function of Ytg iron import system (15) and the iron responsiveness of ytgA expression (15,16).…”

Section: Discussionsupporting

confidence: 71%

“…More recent evidence points to the Ytg system functioning in iron transport. First, the periplasmic substratebinding protein, YtgA, exhibited a significant preference toward iron over zinc or manganese in vitro (15). Also, the transcript expression of ytgA was induced in response to iron starvation of C. trachomatis (16), indicating an iron-dependent regulation of the ytg operon.…”

mentioning

confidence: 98%

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Cleavage of a putative metal permease in Chlamydia trachomatis yields an iron-dependent transcriptional repressor

Thompson

Nicod

Malcolm

et al. 2012

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

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The regulation of iron homeostasis is essential for most organisms, because iron is required for a variety of conserved biochemical processes, yet can be toxic at high concentrations. Upon experiencing iron starvation in vitro, the obligate intracellular human pathogen Chlamydia trachomatis exhibits elevated expression of a putative iron-transport system encoded by the ytg operon. The third component of the ytg operon, CT069 (YtgCR), encodes a protein with two distinct domains: a membrane-anchored metal ion permease and a diphtheria toxin repressor (DtxR)-like transcriptional repressor. In this report, we demonstrate that the C-terminal domain of CT069 (YtgR) serves as an iron-dependent autorepressor of the ytg operon. Moreover, the nascent full-length metal permease-transcriptional repressor protein was processed during the course of infection, and heterologously when expressed in Escherichia coli. The products produced by heterologous cleavage in E. coli were functional in the repression of a reporter gene downstream of a putative YtgR operator. We report a bona fide mechanism of iron-dependent regulation of transcription in Chlamydia. Moreover, the unusual membrane permease-DNA-binding polypeptide fusion configuration was found in several bacteria. Therefore, the DNA-binding capability and liberation of the YtgR domain from a membrane-anchored permease in C. trachomatis could represent a previously uncharacterized mechanism for prokaryotic regulation of iron-homeostasis.ron is an essential micronutrient for nearly all organisms, with its redox capability being both beneficial and harmful to the organism, because of iron readily catalyzing the formation of toxic free radicals via the Haber-Weiss reaction (1). Thus, both eukaryotes and prokaryotes, alike, have evolved regulatory networks for the tight control of intracellular iron homeostasis.In prokaryotes, these regulatory networks are usually controlled through metal-dependent DNA-binding proteins. Two of the best-characterized metal-dependent transcriptional regulators are ferric uptake regulator (Fur) in Escherichia coli and diphtheria toxin repressor (DtxR) in Corynebacterium diphtheriae. Although nonhomologous and structurally distinct, both families of transcriptional repressors function similarly, in that the presence of a cognate metal cofactor activates DNA-binding activity (2). Homodimers of the metal-activated proteins recognize specific cis-regulatory elements that are often located proximally to the promoter operating regions of the regulated gene, effectively blocking RNA polymerase initiation of transcription (3, 4).Chlamydia trachomatis is an obligate, intracellular human pathogen that is responsible for the leading cause of bacterial sexually transmitted infection (5, 6) and infection-derived blindness (7) worldwide. The chlamydial requirement for iron is well established, because iron restriction forces Chlamydia into an alternative persistent growth mode distinguished by abnormal morphology (8-10) and altered transcriptional profile of hall...

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Section: Discussionsupporting

confidence: 71%

mentioning

confidence: 98%

Cleavage of a putative metal permease in Chlamydia trachomatis yields an iron-dependent transcriptional repressor

Thompson

Nicod

Malcolm

et al. 2012

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

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“…The data represent the average Ϯ SD of the results from at least two independent experiments. to CTL0326), annotated as a Mn 2ϩ /Zn 2ϩ ABC metal transporter, has been shown to prefer iron over manganese (61). Taken together, it is plausible that Chlamydia spp.…”

Section: Figmentioning

confidence: 92%

CTL0511 from Chlamydia trachomatis Is a Type 2C Protein Phosphatase with Broad Substrate Specificity

Claywell

Fisher

2016

J Bacteriol

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Protein phosphorylation has become increasingly recognized for its role in regulating bacterial physiology and virulence. Chlamydia spp. encode two validated Hanks'-type Ser/Thr protein kinases, which typically function with cognate protein phosphatases and appear capable of global protein phosphorylation. Consequently, we sought to identify a Ser/Thr protein phosphatase partner for the chlamydial kinases. CTL0511 from Chlamydia trachomatis L2 434/Bu, which has homologs in all sequenced Chlamydia spp., is a predicted type 2C Ser/Thr protein phosphatase (PP2C). Recombinant maltose-binding protein (MBP)-tagged CTL0511 (rCTL0511) hydrolyzed p-nitrophenyl phosphate (pNPP), a generic phosphatase substrate, in a MnCl 2 -dependent manner at physiological pH. Assays using phosphopeptide substrates revealed that rCTL0511 can dephosphorylate phosphorylated serine (P-Ser), P-Thr, and P-Tyr residues using either MnCl 2 or MgCl 2 , indicating that metal usage can alter substrate preference. Phosphatase activity was unaffected by PP1, PP2A, and PP3 phosphatase inhibitors, while mutation of conserved PP2C residues significantly inhibited activity. Finally, phosphatase activity was detected in elementary body (EB) and reticulate body (RB) lysates, supporting a role for protein dephosphorylation in chlamydial development. These findings support that CTL0511 is a metal-dependent protein phosphatase with broad substrate specificity, substantiating a reversible phosphorylation network in C. trachomatis. IMPORTANCEChlamydia spp. are obligate intracellular bacterial pathogens responsible for a variety of diseases in humans and economically important animal species. Our work demonstrates that Chlamydia spp. produce a PP2C capable of dephosphorylating P-Thr, P-Ser, and P-Tyr and that Chlamydia trachomatis EBs and RBs possess phosphatase activity. In conjunction with the chlamydial Hanks'-type kinases Pkn1 and PknD, validation of CTL0511 fulfills the enzymatic requirements for a reversible phosphoprotein network. As protein phosphorylation regulates important cellular processes, including metabolism, differentiation, and virulence, in other bacterial pathogens, these results set the stage for elucidating the role of global protein phosphorylation in chlamydial physiology and virulence. C hlamydia spp. are obligate intracellular bacterial pathogens that are widely distributed in nature and are responsible for significant diseases in humans and a variety of animals (1, 2). The human-specific pathogen Chlamydia trachomatis is the leading cause of preventable blindness and the most common reportable bacterial sexually transmitted infection both in the United States and worldwide (3, 4). C. trachomatis infections of the conjunctiva and the urogenital tract may lead to chronic diseases, including trachoma, pelvic inflammatory disease, and infertility (1). Further understanding of the physiology of these highly significant pathogens is critical for developing therapeutics and vaccines.While Chlamydia spp. differ in host range and virul...

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“…The only component that has been studied in Chlamydia is YtgA, which is a homolog of the periplasmic metal-binding protein TroA. Raulston and coworkers (28) showed that C. trachomatis YtgA bound iron in vitro, and its expression was induced during iron-restrictive growth. The T. pallidum Tro transporter has been shown to import Zn 2ϩ , Mn 2ϩ , and possibly Fe 2ϩ (20), but the metal ions that are transported by the chlamydial Ytg transporter have not yet been determined.…”

Section: Discussionmentioning

confidence: 99%

Identification and Functional Analysis of CT069 as a Novel Transcriptional Regulator in Chlamydia

et al. 2011

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Only a small number of transcription factors have been predicted in Chlamydia spp., which are obligate intracellular bacteria that include a number of important human pathogens. We used a bioinformatics strategy to identify novel transcriptional regulators from the Chlamydia trachomatis genome by predicting proteins with the general structure and characteristic functional domains of a bacterial transcription factor. With this approach, we identified CT069 as a candidate transcription factor with sequence similarity at its C terminus to Treponema pallidum TroR. Like TroR, the gene for CT069 belongs to an operon that encodes components of a putative ABC transporter for importing divalent metal cations. However, CT069 has been annotated as YtgC because of sequence similarity at its N terminus to TroC, a transmembrane component of this metal ion transporter. Instead, CT069 appears to be a fusion protein composed of YtgC and a TroR ortholog that we have called YtgR. Although it has not been previously reported, a similar YtgC-YtgR fusion protein is predicted to be encoded by other Chlamydia spp. and several other bacteria, including Bacillus subtilis. We show that recombinant YtgR polypeptide bound specifically to an operator sequence upstream of the ytg operon and that binding was enhanced by Zn 2؉ . We also demonstrate that YtgR repressed transcription from the ytg promoter in a heterologous in vivo reporter assay. These results provide evidence that CT069 is a negative regulator of the ytg operon, which encodes a putative metal ion transporter in C. trachomatis.

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Chlamydia trachomatis YtgA is an iron-binding periplasmic protein induced by iron restriction

Cited by 27 publications

References 41 publications

Cleavage of a putative metal permease in Chlamydia trachomatis yields an iron-dependent transcriptional repressor

Cleavage of a putative metal permease in Chlamydia trachomatis yields an iron-dependent transcriptional repressor

CTL0511 from Chlamydia trachomatis Is a Type 2C Protein Phosphatase with Broad Substrate Specificity

Identification and Functional Analysis of CT069 as a Novel Transcriptional Regulator in Chlamydia

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