5aeo

Publication Abstract from PubMed

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 beta-barrel fold with beta1-beta2-beta3-beta8-beta5-beta6-beta7-beta4 topology decorated by a single peripheral alpha-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 alpha-helix and a belt around the centre of the beta-barrel. Possible functional significance of these recent structures is discussed.

Structural characterisation of the virulence-associated protein VapG from the horse pathogen Rhodococcus equi.,Okoko T, Blagova EV, Whittingham JL, Dover LG, Wilkinson AJ Vet Microbiol. 2015 Feb 9. pii: S0378-1135(15)00057-7. doi:, 10.1016/j.vetmic.2015.01.027. PMID:25746683^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.