Identification of a bacterial factor required for actin-based motility of Burkholderia pseudomallei.
Stevens, Mark P. 1; Stevens, Joanne M. 1; Jeng, Robert L. 2; Taylor, Lowrie A. 1; Wood, Michael W. 1; Hawes, Pippa 3; Monaghan, Paul 3; Welch, Matthew D. 2; Galyov, Edouard E. 1,*
[Article] Molecular Microbiology. 56(1):40-53, April 2005.

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Summary: Burkholderia pseudomallei is a Gram-negative facultative intracellular pathogen that enters and escapes from eukaryotic cells using the power of actin polymerization. We have identified a bacterial protein (BimA) that is required for the ability of B. pseudomallei to induce the formation of actin tails. BimA contains proline-rich motifs and WH2-like domains and shares limited homology at the C-terminus with the Yersinia autosecreted adhesin YadA. BimA is located at the pole of the bacterial cell at which actin polymerization occurs and mutation of bimA abolished actin-based motility of the pathogen in J774.2 cells. Transient expression of BimA in HeLa cells resulted in F-actin clustering reminiscent of that seen on WASP overexpression. Antibody-mediated clustering of a CD32 chimera in which the cytoplasmic domain was replaced with BimA resulted in localization of the chimera to the tips of F-actin enriched membrane protrusions. We report that purified truncated BimA protein binds monomeric actin in a concentration-dependent manner in cosedimentation assays and that BimA stimulates actin polymerization in vitro in a manner independent of the cellular Arp2/3 complex.

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