Overproduction of the bacterial flagellar switch proteins and their interactions with the MS ring complex in vitro

Ultracentrifugation and gel electrophoresis studies reveal that during the interaction of flagellar switch proteins FliG, FliM and FliN of S. typhimurium with MS ring complexes constituting HiF proteins, FliG binds to MS ring complex at 1:1 molar ratio whereas FliM binds att 1:5 molar ratio. This shows that the binding sites for FliM on MS ring are limited. FliN does not bind to MS ring complexes. The interaction of switch proteins with MS ring complex leads to flagellar rotation.