Characterizing a potential β-barrel assembly machinery (BAM) complex in Treponema pallidum

Date

2011-10-18

Authors

Cummings, Michael

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Abstract

Previous experimentation using differential immunological screening identified Tp0326, a protein predicted to be located in the outer membrane (OM) of the bacterium Treponema pallidum. This protein is homologous to BamA members of the β-barrel assembly machinery (BAM) family of proteins, which are conserved throughout pathogenic Gram-negative bacteria. In Escherichia coli the BAM proteins are found as a complex composed of five proteins: BamA, which is an integral membrane protein, and four accessory lipoproteins, BamB - BamE, which localize to the inner leaflet of the outer membrane. In E. coli BamA has been shown to mediate the insertion and assembly of proteins in the OM via interaction with the BAM complex and periplasmic chaperones (SurA, Skp, and DegP). We hypothesize that a similar OMP translocation complex exists within T. pallidum and that this complex is responsible for ushering T. pallidum OMPs to the bacterial surface. Characterization of the putative T. pallidum OMP transport machinery was performed by bioinformatic analyses and protein-protein interaction studies. Protein-protein interaction studies included screening a T. pallidum Lambda genomic expression library with recombinant T. pallidum protein Tp0326 and Far-Western blotting techniques. Using bioinformatic analyses we have identified putative T. pallidum homologues of the E. coli lipoproteins BamD (Tp0622) and BamB (Tp0133) as well as putative homologues of the E. coli chaperone proteins Skp (Tp0327) and DegP (Tp0773). The T. pallidum Lambda genomic expression library screen identified the putative E. coli BamD homologue (Tp0622), which was originally discovered through bioinformatic analyses. The expression library screen also identified two putative T. pallidum OMPs (Tp0750 and Tp0751) as potential interaction partners of Tp0326. Combined bioinformatic analyses and protein-protein interaction studies provide evidence a BAM complex may exist within T. pallidum, and similar to E. coli, this complex may be involved in ushering T. pallidum OMPs to the bacterial surface.

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Keywords

protein, proteins, genomic

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