Characterization of the Che7 System of Myxococcus xanthus
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Myxococcus xanthus is a Gram negative soil bacterium that utilizes eight chemosensory systems of interacting proteins, most of which are homologous to the E.coli chemotaxis proteins, in order to regulate its two types of gliding motility (A and S), predation of other organisms, and multicellular fruiting body formation. The M. xanthus Che7 system, which has not been thoroughly characterized to date, is of specific interest because it is thought to regulate A motility through exopolysaccharide (EPS) production, contain a completely cytoplasmic Mcp (methyl-accepting chemotaxis protein), and have two functioning non-chemotaxis proteins: Cpc7 and Des7. In this study, we explored the protein-protein interactions of the Che7 system of M. xanthus through yeast two-hybrid and beta-galactosidase assays. In addition to the expected interactions between the Che7 chemotaxis homologs, we found that Cpc7 interacted with both Des7 and Mcp7. This suggests that Cpc7 is cytoplasmic and that several possibilities for the mechanism of signal transduction in the Che7 system of M. xanthus exist. From these results, we propose a new protein interaction model for the Che7 chemosensory two-component signal transduction system.