Analysing protein-protein interactions of the Myxococcus xanthus Dif signalling pathway using the yeast two-hybrid system.

The dif operon is essential for fruiting body formation, fibril (exopolysaccharide) production and social motility of Myxococcus xanthus. The dif locus contains a gene cluster homologous to chemotaxis genes such as mcp (difA), cheW (difC), cheY (difD), cheA (difE) and cheC (difF), as well as an unknown ORF called difB. This study used yeast two-hybrid analysis to investigate possible interactions between Dif proteins, and determined that DifA, C, D and E interact in a similar fashion to chemotaxis proteins of Escherichia coli and Bacillus subtilis. It also showed that DifF interacted with DifD, and that the novel protein DifB did not interact with Dif proteins. Furthermore, DifA-F proteins were used to determine other possible protein-protein interactions in the M. xanthus genomic library. The authors not only confirmed the specific interactions among known Dif proteins, but also discovered two novel interactions between DifE and Nla19, and DifB and YidC, providing some new information about the Dif signalling pathway. Based on these findings, a model for the Dif signalling pathway is proposed.