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Structural characterisation of the virulence-associated protein VapG from the horse pathogen Rhodococcus equi.


ABSTRACT: Virulence and host range in Rhodococcus equi depends on the variable pathogenicity island of their virulence plasmids. Notable gene products are a family of small secreted virulence-associated proteins (Vaps) that are critical to intramacrophagic proliferation. Equine-adapted strains, which cause severe pyogranulomatous pneumonia in foals, produce a cell-associated VapA that is necessary for virulence, alongside five other secreted homologues. In the absence of biochemical insight, attention has turned to the structures of these proteins to develop a functional hypothesis. Recent studies have described crystal structures for VapD and a truncate of the VapA orthologue of porcine-adapted strains, VapB. Here, we crystallised the full-length VapG and determined its structure by molecular replacement. Electron density corresponding to the N-terminal domain was not visible suggesting that it is disordered. The protein core adopted a compact elliptical, anti-parallel ?-barrel fold with ?1-?2-?3-?8-?5-?6-?7-?4 topology decorated by a single peripheral ?-helix unique to this family. The high glycine content of the protein allows close packing of secondary structural elements. Topologically, the surface has no indentations that indicate a nexus for molecular interactions. The distribution of polar and apolar groups on the surface of VapG is markedly uneven. One-third of the surface is dominated by exposed apolar side-chains, with no ionisable and only four polar side-chains exposed, giving rise to an expansive flat hydrophobic surface. Other surface regions are more polar, especially on or near the ?-helix and a belt around the centre of the ?-barrel. Possible functional significance of these recent structures is discussed.

SUBMITTER: Okoko T 

PROVIDER: S-EPMC4518536 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature

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Structural characterisation of the virulence-associated protein VapG from the horse pathogen Rhodococcus equi.

Okoko Tebekeme T   Blagova Elena V EV   Whittingham Jean L JL   Dover Lynn G LG   Wilkinson Anthony J AJ  

Veterinary microbiology 20150209 1-2


Virulence and host range in Rhodococcus equi depends on the variable pathogenicity island of their virulence plasmids. Notable gene products are a family of small secreted virulence-associated proteins (Vaps) that are critical to intramacrophagic proliferation. Equine-adapted strains, which cause severe pyogranulomatous pneumonia in foals, produce a cell-associated VapA that is necessary for virulence, alongside five other secreted homologues. In the absence of biochemical insight, attention has  ...[more]

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