Structure of EspB from the ESX-1 Type VII Secretion System and Insights into its Export Mechanism

Solomonson, Matthew; Setiaputra, Dheva; Makepeace, Karl A.T.; Lameignère, Emilie; Petrotchenko, Evgeniy V.; Conrady, Deborah G.; Bergeron, Julien R. C.; Vuckovic, M.; DiMaio, Frank; Borchers, Christoph H.; Yip, Calvin K.; Strynadka, N.C.J.

doi:10.1016/j.str.2015.01.002

Cited by 86 publications

(121 citation statements)

References 63 publications

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“…A recent structural study of EspB, an M. tuberculosis protein secreted by the ESX-1 type VII secretion system, revealed that this protein adopts a conformation similar to that of the PE25/PPE41 structure and forms ring-shaped multimers (54). PE19 and its PPE partner(s) may form similar multimers that localize to the cell wall and influence its permeability.…”

Section: Discussionmentioning

confidence: 99%

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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Section: Discussionmentioning

confidence: 99%

Mycobacterium tuberculosis Resists Stress by Regulating PE19 Expression

et al. 2016

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“…In conclusion, this study provides a better understanding of ESX-specific substrates and lays the groundwork for characterization of EspB and MycP 1 functions in the context of ESX secretion. While this manuscript was under review, Solomonson et al reported crystal structure of Mycobacterium smegmatis EspB homolog (Solomonson et al, 2015). The structures of M. tuberculosis and M. smegmatis EspB display the same fold (2.1–2.3 Å r.m.s.d.…”

Section: Discussionmentioning

confidence: 99%

Structure of EspB, a secreted substrate of the ESX-1 secretion system of Mycobacterium tuberculosis

Korotkova

Piton

Wagner

et al. 2015

Journal of Structural Biology

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Mycobacterium tuberculosis secretes multiple virulence factors during infection via the general Sec and Tat pathways, and via specialized ESX secretion systems, also referred to as type VII secretion systems. The ESX-1 secretion system is an important virulence determinant because deletion of ESX-1 leads to attenuation of M. tuberculosis. ESX-1 secreted protein B (EspB) contains putative PE (Pro-Glu) and PPE (Pro-Pro-Glu) domains, and a C-terminal domain, which is processed by MycP1 protease during secretion. We determined the crystal structure of PE–PPE domains of EspB, which represents an all-helical, elongated molecule closely resembling the structure of the PE25–PPE41 heterodimer despite limited sequence similarity. Also, we determined the structure of full-length EspB, which does not have interpretable electron density for the C-terminal domain confirming that it is largely disordered. Comparative analysis of EspB in cell lysate and culture filtrates of M. tuberculosis revealed that mature secreted EspB forms oligomers. Electron microscopy analysis showed that the N-terminal fragment of EspB forms donut-shaped particles. These data provide a rationale for the future investigation of EspB's role in M. tuberculosis pathogenesis.

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“…TIC110 is a component of the chloroplast protein import complex (24). EspB from Mycobacterium tuberculosis and LegC3 from Legionella pneumophila are bacterial effector proteins causing phagosome rupture or preventing phagosome fusion with lysosomes, respectively, after uptake into the host cell (25,26). The Bro1V domain is part of the yeast Bro1 protein which is homologous to the human Alix (ALG-2-interacting protein X) protein.…”

Section: Ndgd1 Is Essential For Dgdg Mobilization From the Oem To Thementioning

confidence: 99%

Synthesis and transfer of galactolipids in the chloroplast envelope membranes of Arabidopsis thaliana

Kelly

Kalisch

Hölzl

et al. 2016

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

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Galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)] are the hallmark lipids of photosynthetic membranes. The galactolipid synthases MGD1 and DGD1 catalyze consecutive galactosyltransfer reactions but localize to the inner and outer chloroplast envelopes, respectively, necessitating intermembrane lipid transfer. Here we show that the N-terminal sequence of DGD1 (NDGD1) is required for galactolipid transfer between the envelopes. Different diglycosyllipid synthases (DGD1, DGD2, and Chloroflexus glucosyltransferase) were introduced into the dgd1-1 mutant of Arabidopsis in fusion with N-terminal extensions (NDGD1 and NDGD2) targeting to the outer envelope. Reconstruction of DGDG synthesis in the outer envelope membrane was observed only with diglycosyllipid synthase fusion proteins carrying NDGD1, indicating that NDGD1 enables galactolipid translocation between envelopes. NDGD1 binds to phosphatidic acid (PA) in membranes and mediates PA-dependent membrane fusion in vitro. These findings provide a mechanism for the sorting and selective channeling of lipid precursors between the galactolipid pools of the two envelope membranes.galactolipid | chloroplast | envelope | lipid transfer T he two galactolipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), are most abundant in land plants, green algae, and cyanobacteria (1). MGDG and DGDG are predominant in thylakoid membranes of chloroplasts, where they are integral components of photosystems I and II and of the light-harvesting complex II (2-4), and are essential for photosynthesis and growth (5, 6). Galactolipids are synthesized in the envelope membranes of chloroplasts (7). In tobacco and Arabidopsis, the MGDG synthase MGD1 localizes to the inner envelope where it produces the major proportion of MGDG (8, 9). The outer chloroplast envelope of Arabidopsis harbors two DGDG synthases, DGD1 and DGD2 (10, 11). DGD1 synthesizes the predominant proportion of DGDG, whereas DGD2 is active during growth under phosphate limitation. Phosphate deprivation results in the accumulation of glycolipids, including DGDG, at the expense of phospholipids and the redirection of phosphate to other cellular processes (12). DGDG synthesized by DGD1 and DGD2 is transported to thylakoid and extraplastidial membranes, respectively (11,12).Transport processes are required to channel lipid molecules between organelles and across and between different membranes (13). An ATP-binding cassette (ABC) transporter composed of three different subunits [trigalactosyldiacylglycerol1 (TGD1), -2 (TGD2), and -3 (TGD3)] is involved in the transfer of lipid precursors from the endoplasmic reticulum (ER) to the chloroplast where they are used for galactolipid synthesis. Galactolipid molecules derived from imported precursors can be distinguished from galactolipids directly synthesized in the chloroplast by the acyl composition at the sn2 position of the glycerol, with molecules containing sn2-16C acyl groups being chloroplast-derived (prokaryotic...

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Structure of EspB from the ESX-1 Type VII Secretion System and Insights into its Export Mechanism

Cited by 86 publications

References 63 publications

Mycobacterium tuberculosis Resists Stress by Regulating PE19 Expression

Mycobacterium tuberculosis Resists Stress by Regulating PE19 Expression

Structure of EspB, a secreted substrate of the ESX-1 secretion system of Mycobacterium tuberculosis

Synthesis and transfer of galactolipids in the chloroplast envelope membranes of Arabidopsis thaliana

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