Structures of F(420)H(2):NADP(+) oxidoreductase with and without its substrates bound

Cofactor F(420) is a 5′-deazaflavin derivative first discovered in methanogenic archaea but later found also to be present in some bacteria. As a coenzyme, it is involved in hydride transfer reactions and as a prosthetic group in the DNA photolyase reaction. We report here for the first time on the crystal structure of an F(420)-dependent oxidoreductase bound with F(420). The structure of F(420)H(2):NADP(+) oxidoreductase resolved to 1.65 Å contains two domains: an N-terminal domain characteristic of a dinucleotide-binding Rossmann fold and a smaller C-terminal domain. The nicotinamide and the deazaflavin part of the two coenzymes are bound in the cleft between the domains such that the Si-faces of both face each other at a distance of 3.1 Å, which is optimal for hydride transfer. Comparison of the structures bound with and without substrates reveals that of the two substrates NADP has to bind first, the binding being associated with an induced fit.