Identification of a novel two-partner secretion system from Burkholderia pseudomallei
2004
Brown, N. F. | Logue, C.-A. | Boddey, J. A. | Scott, R. | Hirst, R. G. | Beacham, I. R.
Two adjacent genes, bpaA and bpaB, whose products display significant similarity to a number of two-partner secretion (TPS) systems have been identified in Burkholderia pseudomallei strain 08, but are absent from the closely related avirulent species B. thailandensis. They possess a number of sequence features characteristic of TPS systems, including the presence of an NPNGI motif in a region of BpaA which strongly resembles a TPS secretion domain. BpaA is a very large protein (~530 kDa) and contains three repeats, each 600–800-amino acids long. Putative membrane-spanning regions in BpaB were identified through alignment with TpsB family members, and this also revealed an N-terminal extension not found in other TpsB proteins. The bpaA gene was found to be absent from the majority of B. pseudomallei strains. It appears that bpaAB are located within a putative genomic island that is inserted in close proximity to a methionine tRNACᴬᵀ-encoding gene. Expression of BpaA was undetectable in cells grown in laboratory media. However, owing to the similarity of BpaA to known adhesin molecules, a potential role of BpaA in virulence was investigated in cell culture and in an animal model, but no evidence for such a role was found in these test systems.
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