Protein-protein association and cellular localization of four essential gene products encoded by tellurite resistance-conferring cluster "ter" from pathogenic Escherichia coli.

Gene cluster "ter" conferring high tellurite resistance has been identified in various pathogenic bacteria including Escherichia coli O157:H7. However, the precise mechanism as well as the molecular function of the respective gene products is unclear. Here we describe protein-protein association and localization analyses of four essential Ter proteins encoded by minimal resistance-conferring fragment (terBCDE) by means of recombinant expression. By using a two-plasmid complementation system we show that the overproduced single Ter proteins are not able to mediate tellurite resistance, but all Ter members play an irreplaceable role within the cluster. We identified several types of homotypic and heterotypic protein-protein associations among the Ter proteins by in vitro and in vivo pull-down assays and determined their cellular localization by cytosol/membrane fractionation. Our results strongly suggest that Ter proteins function involves their mutual association, which probably happens at the interface of the inner plasma membrane and the cytosol.

Study of membrane attachment and in vivo co-localization of TerB protein from uropathogenic Escherichia coli KL53.

The tellurite resistance operon has been found in a wide range of bacteria. We have previously identified the ter operon (terXYW and terZABCDEF) of the uropathogenic strain Escherichia coli KL53. In this study, we use an innovative approach to identify putative protein-protein interaction partners for one of the essential tellurite resistance proteins - TerB. We observe that N-terminus of TerB attaches to the periplasmic membrane, while the C-terminus is partly localized in the cytoplasm. Subsequently, by methods of in vivo cross-linking and mass-spectroscopic analysis, we have determined the proteins from both the membrane and cytoplasmic fractions, which can potentially interact with TerB.