Bipartite Topology of Treponema pallidum Repeat Proteins C/D and I

Anand, Asha; LeDoyt, Morgan; Karanian, Carson; Luthra, Amit; Koszelak-Rosenblum, Mary; Malkowski, Michael G.; Puthenveetil, Robbins; Vinogradova, Olga; Radolf, Justin D.

doi:10.1074/jbc.m114.629188

Cited by 31 publications

(49 citation statements)

References 101 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The conceptual breakthrough in our quest for T. pallidum rare OMPs was the use of a structural bioinformatics approach to mine the spirochete's genome for proteins predicted to adopt a ␤-barrel conformation; TP_0326/BamA, the only OMP in T. pallidum related to OMPs in Gram-negative bacteria, emerged as a top candidate in the putative T. pallidum OM proteome (29). The finding of BamA (29) and subsequently a BAM complex (34) implied the existence of other ␤-barrel OMPs which serve as substrates for the OM biogenesis machinery, a supposition confirmed by biophysical characterization and surface localization of the T. pallidum repeat C (TprC) subfamily of proteins (42,62). Because TP_0326 resides constitutively at the hostpathogen interface, one might anticipate that its involvement in the disease process extends beyond its role in OM biogenesis.…”

Section: Discussionmentioning

confidence: 80%

A Homology Model Reveals Novel Structural Features and an Immunodominant Surface Loop/Opsonic Target in the Treponema pallidum BamA Ortholog TP_0326

et al. 2015

Self Cite

View full text Add to dashboard Cite

We recently demonstrated that TP_0326 is a bona fide rare outer membrane protein (OMP) in Treponema pallidum and that it possesses characteristic BamA bipartite topology. Herein, we used immunofluorescence analysis (IFA) to show that only the ␤-barrel domain of TP_0326 contains surface-exposed epitopes in intact T. pallidum. Using the solved structure of Neisseria gonorrhoeae BamA, we generated a homology model of full-length TP_0326. Although the model predicts a typical BamA fold, the ␤-barrel harbors features not described in other BamAs. Structural modeling predicted that a dome comprised of three large extracellular loops, loop 4 (L4), L6, and L7, covers the barrel's extracellular opening. L4, the dome's major surface-accessible loop, contains mainly charged residues, while L7 is largely neutral and contains a polyserine tract in a two-tiered conformation. L6 projects into the ␤-barrel but lacks the VRGF/Y motif that anchors L6 within other BamAs. IFA and opsonophagocytosis assay revealed that L4 is surface exposed and an opsonic target. Consistent with B cell epitope predictions, immunoblotting and enzyme-linked immunosorbent assay (ELISA) confirmed that L4 is an immunodominant loop in T. pallidum-infected rabbits and humans with secondary syphilis. Antibody capture experiments using Escherichia coli expressing OM-localized TP_0326 as a T. pallidum surrogate further established the surface accessibility of L4. Lastly, we found that a naturally occurring substitution (Leu 593 ¡ Gln 593 ) in the L4 sequences of T. pallidum strains affects antibody binding in sera from syphilitic patients. Ours is the first study to employ a "structure-to-pathogenesis" approach to map the surface topology of a T. pallidum OMP within the context of syphilitic infection. IMPORTANCEPreviously, we reported that TP_0326 is a bona fide rare outer membrane protein (OMP) in Treponema pallidum and that it possesses the bipartite topology characteristic of a BamA ortholog. Using a homology model as a guide, we found that TP_0326 displays unique features which presumably relate to its function(s) in the biogenesis of T. pallidum's unorthodox OM. The model also enabled us to identify an immunodominant epitope in a large extracellular loop that is both an opsonic target and subject to immune pressure in a human population. Ours is the first study to follow a structure-to-pathogenesis approach to map the surface topology of a T. pallidum rare OMP within the context of syphilitic infection. W ithin the outer membranes (OMs) of Gram-negative bacteria is a unique class of integral membrane proteins that fold into a ␤-barrel structure consisting of 8 to 26 antiparallel amphipathic ␤ strands; typically, extensive hydrogen bonding between the first and last strands closes and stabilizes the barrel, often creating a central channel (1, 2). ␤-Barrel outer membrane proteins (OMPs) have two principal functions: (i) insertion/transport of proteins into or across the OM and (ii) formation of aqueous pores for the passive or selective uptake of...

show abstract

Section: Discussionmentioning

confidence: 80%

A Homology Model Reveals Novel Structural Features and an Immunodominant Surface Loop/Opsonic Target in the Treponema pallidum BamA Ortholog TP_0326

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…The native proteins are low in abundance (~200 copies per cell), surface-exposed, and amphiphilic, whereas the folded recombinants form β-sheet-rich, heat-modifiable trimers that readily insert into artificial membranes. Similar to MOSP 61 , integration of TprC/D and TprI into liposomes results in permeability increases comparable to those produced by the archetypal porin, E. coli OmpF 59,60 . Formation of large, non-selective channels could explain how these rare proteins function cooperatively to meet the spirochete’s nutritional needs.…”

Section: The Face Of Stealth-the Outer Membranementioning

confidence: 83%

“…As an alternative to genome mining for OMP orthologs, we used a computational matrix to identify proteins predicted to adopt the hallmark conformation of an OMP, the β-barrel 57 . The two highest ranked Tprs, TprC/D (TprC (TP0117) and TprD (TP0131) are identical in the Nichols strain) and TprI (TP0620), possess all of the properties expected of a rare OMP 59,60 . The native proteins are low in abundance (~200 copies per cell), surface-exposed, and amphiphilic, whereas the folded recombinants form β-sheet-rich, heat-modifiable trimers that readily insert into artificial membranes.…”

Section: The Face Of Stealth-the Outer Membranementioning

confidence: 99%

Treponema pallidum, the syphilis spirochete: making a living as a stealth pathogen

et al. 2016

Self Cite

View full text Add to dashboard Cite

The last two decades have seen a worldwide resurgence in infections caused by Treponema pallidum subsp. pallidum, the syphilis spirochete. The syphilis spirochete’s well-recognized capacity for early dissemination and immune evasion has earned it the designation ‘the stealth pathogen’. Despite the many hurdles to studying syphilis pathogenesis, most notably the inability to culture and to genetically manipulate T. pallidum, in recent years, considerable progress has been made in elucidating the structural, physiologic, and regulatory facets of stealth pathogenicity. In this Review, we integrate this eclectic body of information to garner fresh insights into the highly successful parasitic lifestyles of the syphilis spirochete and related pathogenic treponemes.

show abstract

“…Two other Tpr proteins, TprC and TprI, have met stringent experimental criteria for rare outer membrane proteins. They form trimeric β-barrels when refolded in vitro , cause large increases in permeability upon insertion into liposomes and are surface-exposed opsonic targets in T. pallidum 93,94 . Unlike classic porins, for which the entire polypeptide forms a β-barrel, TprC and TprI are bipartite.…”

Section: Mechanisms/pathophysiologymentioning

confidence: 99%

“…Shown in the outer membrane are TP0751 (as known as pallilysin) 79,81 and Tpp17 (also known as TP0435) 82,241 — two surface-exposed lipoproteins; TP0453, a lipoprotein attached to the inner leaflet of the outer membrane 83 ; BamA (also known as TP0326) 84,94 ; a full-length T. pallidum repeat (Tpr) attached by its N-terminal portion to the peptidoglycan 93,94 ; and a generic β-barrel that represents other non-Tpr outer-membrane proteins identified by computational mining of the T. pallidum genome 112 . Substrates and nutrients present in high concentration in the extracellular milieu (such as, glucose) traverse the outer membrane through porins, such as TprC.…”

Section: Figurementioning

confidence: 99%

Syphilis

Peeling

Mabey

Kamb

et al. 2017

Nat Rev Dis Primers

Self Cite

491

387

View full text Add to dashboard Cite

Treponema pallidum subspecies pallidum (T. pallidum) causes syphilis via sexual exposure or vertical transmission during pregnancy. T. pallidum is renowned for its invasiveness and immune-evasiveness; its clinical manifestations result from local inflammatory responses to replicating spirochetes and often imitate those of other diseases. The spirochete has a long latent period during which patients have no signs or symptoms, but can remain infectious. Despite the availability of simple diagnostic tests and the effectiveness of treatment with a single dose of long-acting penicillin, syphilis is re-emerging as a global public health problem, particularly among men who have sex with men (MSM) in high-income and middle-income countries. Syphilis also causes several hundred thousand stillbirths and neonatal deaths every year in developing nations. Although several low-income countries have achieved WHO targets for the elimination of congenital syphilis, an alarming increase of syphilis in HIV-infected MSM serves as a strong reminder of the tenacity of T. pallidum as a pathogen. Strong advocacy and community involvement is needed to ensure that syphilis is given high priority on the global health agenda. More investment in research is needed on the interaction between HIV and syphilis in MSM, as well as into improved diagnostics, a better test of cure, intensified public health measures and, ultimately, a vaccine.

show abstract

Bipartite Topology of Treponema pallidum Repeat Proteins C/D and I

Cited by 31 publications

References 101 publications

A Homology Model Reveals Novel Structural Features and an Immunodominant Surface Loop/Opsonic Target in the Treponema pallidum BamA Ortholog TP_0326

A Homology Model Reveals Novel Structural Features and an Immunodominant Surface Loop/Opsonic Target in the Treponema pallidum BamA Ortholog TP_0326

Treponema pallidum, the syphilis spirochete: making a living as a stealth pathogen

Syphilis

Contact Info

Product

Resources

About