Methionine synthase reductase (MTRR) is involved in reducing cob(II)alamin (B12r) to cob(I)alamin (B12s), the cofactor form used by methionine synthase (MTR). MTRR requires 1 FMN and 1 FAD per subunit for activity (Wolthers et al. 2007). MTRR exists a stable complex with MTR, bound through their FMN-binding and C-terminal activation domains respectively (Wolthers & Scrutton 2007, Wolthers & Scrutton 2009).
