The PPE Domain of PPE17 Is Responsible for Its Surface Localization and Can Be Used to Express Heterologous Proteins on the Mycobacterial Surface

Donà, Valentina; Ventura, Marcello; Sali, Michela; Cascioferro, Alessandro; Provvedi, Roberta; Palù, Giorgio; Delogu, Giovanni; Manganelli, Riccardo

doi:10.1371/journal.pone.0057517

Cited by 25 publications

(20 citation statements)

References 28 publications

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“…On the basis of these observations, it has been proposed that these PE and PPE proteins are exported as folded heterodimers in M. tuberculosis (28, 32) with their final localization either at the cell surface of M. tuberculosis and/or in the culture medium (33). Flow cytometry experiments showed that PPE36 is a surface-accessible protein consistent with previous observations for several other PPE proteins (34, 35). PPE36 is exclusively associated with membranes in subcellular fractionation experiments in contrast to PPE62 and Rv0265c.…”

Section: Discussionsupporting

confidence: 89%

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PPE Surface Proteins Are Required for Heme Utilization by Mycobacterium tuberculosis

Mitra

Speer

Lin

et al. 2017

mBio

127

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Iron is essential for replication of Mycobacterium tuberculosis, but iron is efficiently sequestered in the human host during infection. Heme constitutes the largest iron reservoir in the human body and is utilized by many bacterial pathogens as an iron source. While heme acquisition is well studied in other bacterial pathogens, little is known in M. tuberculosis. To identify proteins involved in heme utilization by M. tuberculosis, a transposon mutant library was screened for resistance to the toxic heme analog gallium(III)-porphyrin (Ga-PIX). Inactivation of the ppe36, ppe62, and rv0265c genes resulted in resistance to Ga-PIX. Growth experiments using isogenic M. tuberculosis deletion mutants showed that PPE36 is essential for heme utilization by M. tuberculosis, while the functions of PPE62 and Rv0265c are partially redundant. None of the genes restored growth of the heterologous M. tuberculosis mutants, indicating that the proteins encoded by the genes have separate functions. PPE36, PPE62, and Rv0265c bind heme as shown by surface plasmon resonance spectroscopy and are associated with membranes. Both PPE36 and PPE62 proteins are cell surface accessible, while the Rv0265c protein is probably located in the periplasm. PPE36 and PPE62 are, to our knowledge, the first proline-proline-glutamate (PPE) proteins of M. tuberculosis that bind small molecules and are involved in nutrient acquisition. The absence of a virulence defect of the ppe36 deletion mutant indicates that the different iron acquisition pathways of M. tuberculosis may substitute for each other during growth and persistence in mice. The emerging model of heme utilization by M. tuberculosis as derived from this study is substantially different from those of other bacteria.

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Section: Discussionsupporting

confidence: 89%

“…It is also unknown whether PPE36 requires PE22 for heme binding and/or uptake. PPE17 is a PPE protein that does not require its cognate PE proteins for stability and surface localization (35). Further experiments are needed to examine whether this is the case for PPE36.…”

Section: Discussionmentioning

confidence: 99%

PPE Surface Proteins Are Required for Heme Utilization by Mycobacterium tuberculosis

Mitra

Speer

Lin

et al. 2017

mBio

127

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“…Since some PE and PPE proteins are known to localize to the mycobacterial cell wall (3,7,8,34,36), we predicted that overexpression of pe19 contributes to stress sensitivity by altering the permeability of the cell envelope. To test this hypothesis, we used an ethidium bromide uptake assay which measures the in- FIG 7 ⌬ppe25-ppe26 and ⌬pe32-ppe65 deletions do not suppress sensitivity of the ⌬pstA1 mutant to acidic pH stress.…”

Section: Resultsmentioning

confidence: 99%

“…Since many PE and PPE proteins that have been characterized to date are localized to the cell wall (3,7,8,(34)(35)(36), we predicted that the aberrant overexpression of these proteins would sensitize M. tuberculosis to stress. We demonstrate that the overexpression of the PE protein PE19, which consists of only a 99-amino-acid PE domain, causes sensitivity to specific cell wall and oxidative stress conditions in vitro and to NOS2-independent host immune responses in vivo.…”

Section: Discussionmentioning

confidence: 99%

“…Among this set of genes, there were several that encode PE and PPE proteins. Of the PE and PPE proteins that have been characterized to date, many are localized to the mycobacterial cell wall (3,7,8,(34)(35)(36). We hypothesized that the overexpression of cell wall-localized PE and/or PPE proteins in the ⌬pstA1 mutant sensitize these bacteria to stress by subtly altering the architecture or permeability of the cell wall.…”

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confidence: 99%

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Mycobacterium tuberculosis Resists Stress by Regulating PE19 Expression

et al. 2016

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cMycobacterium tuberculosis requires the phosphate-sensing signal transduction system Pst/SenX3-RegX3 to resist host immune responses. A ⌬pstA1 mutant lacking a Pst phosphate uptake system component is hypersensitive to diverse stress conditions in vitro and is attenuated in vivo due to constitutive expression of the phosphate starvation-responsive RegX3 regulon. Transcriptional profiling of the ⌬pstA1 mutant revealed aberrant expression of certain pe and ppe genes. PE and PPE proteins, defined by conserved N-terminal domains containing Pro-Glu (PE) or Pro-Pro-Glu (PPE) motifs, account for a substantial fraction of the M. tuberculosis genome coding capacity, but their functions are largely uncharacterized. Because some PE and PPE proteins localize to the cell wall, we hypothesized that overexpression of these proteins sensitizes M. tuberculosis to stress by altering cell wall integrity. To test this idea, we deleted pe and ppe genes that were overexpressed by ⌬pstA1 bacteria. Deletion of a single pe gene, pe19, suppressed hypersensitivity of the ⌬pstA1 mutant to both detergent and reactive oxygen species. Ethidium bromide uptake assays revealed increased envelope permeability of the ⌬pstA1 mutant that was dependent on PE19. The replication defect of the ⌬pstA1 mutant in NOS2 ؊/؊ mice was partially reversed by deletion of pe19, suggesting that increased membrane permeability due to PE19 overexpression sensitizes M. tuberculosis to host immunity. Our data indicate that PE19, which comprises only a 99-amino-acid PE domain, has a unique role in the permeability of the M. tuberculosis envelope that is regulated to resist stresses encountered in the host. O ver 15 years ago, the novel PE and PPE protein families were identified in the complete genome sequence of Mycobacterium tuberculosis; together, these proteins represent over 7% of the genome coding capacity (1). Despite the attention placed on these protein families, their functions remain largely uncharacterized. PE and PPE proteins are defined by conserved N-terminal domains of ϳ110 or ϳ180 amino acids that contain Pro-Glu (PE) or Pro-Pro-Glu (PPE) sequence motifs, respectively (1). Although PE and PPE proteins can be identified in the genomes of all sequenced members of the Mycobacterium genus, their expansion into large multiprotein families is restricted to the slow-growing pathogenic mycobacterial species, including M. tuberculosis, and associated with the expansion of the ESX type VII secretion systems (2). There is evidence that some PE and PPE proteins are exported to the bacterial cell surface or extracellular milieu in an ESX-dependent manner (3-6). ESX-dependent export requires specific sequences within the PE or PPE domain (7, 8), including a recently described YxxxD/E ESX secretion targeting motif located near the C terminus of the ϳ110-amino-acid PE domain (9).The 99 PE proteins and 69 PPE proteins encoded by the M. tuberculosis H37Rv genome can be further divided into subfamilies based on C-terminal sequence motifs (2). The PE_PGRS (polymorphic GC-...

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Immunoregulatory functions and expression patterns of PE/PPE family members: Roles in pathogenicity and impact on anti‐tuberculosis vaccine and drug design

2015

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The Mycobacterium tuberculosis genome was sequenced more than 15 years ago. It revealed a lot of interesting information, one of which was that 10% of the total coding capacity of the M. tuberculosis genome is dedicated to the PE/PPE family. There is a gradual expansion of these proteins from nonpathogenic to pathogenic mycobacteria, and there is increasing evidence that PE/PPE proteins play important roles in mycobacterial pathogenesis. In this review, we discuss PE/ PPE proteins, their close functional association with the ESX clusters, their immunomodulatory functions, and their important roles in mycobacterial virulence. In addition, we have attempted to review and compile information available in the literature detailing the expression patterns of PE/PPE family members in different mycobacterial species and also during infection. Our attempt has been to provide a succinct overview of this interesting family.

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The PPE Domain of PPE17 Is Responsible for Its Surface Localization and Can Be Used to Express Heterologous Proteins on the Mycobacterial Surface

Cited by 25 publications

References 28 publications

PPE Surface Proteins Are Required for Heme Utilization by Mycobacterium tuberculosis

PPE Surface Proteins Are Required for Heme Utilization by Mycobacterium tuberculosis

Mycobacterium tuberculosis Resists Stress by Regulating PE19 Expression

Immunoregulatory functions and expression patterns of PE/PPE family members: Roles in pathogenicity and impact on anti‐tuberculosis vaccine and drug design

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