Interaction of Escherichia coli cobalamin-dependent methionine synthase and its physiological partner flavodoxin: binding of flavodoxin leads to axial ligand dissociation from the cobalamin cofactor

The interaction between flavodoxin and methionine synthase in Escherichia coli was investigated. A 1:1 complex of flavodoxin with methionine synthase showed modifications in both the visible absorbance and electron paramagnetic resonance spectra of the methionine synthase-bound cobalamin cofactor. These spectral changes are indicative of a change in coordination geometry of the cobalt in the bound cobalamin. Findings showed that E. coli flavodoxin not only provides electrons for the activation of methionine synthase but may also cause a global conformation change within methionine synthase when it binds.