Structures of F420H2 : NADP(+) oxidoreductase with and without its substrates bound

Cofactor F-420 is a 5'-deazaflavin derivative first discovered in methanoge nic archaea but later found also to be present in some bacteria. As a coenz yme, 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 c rystal structure of an F-420-dependent oxidoreductase bound with F-420. The structure of F420H2:NADP(+) oxidoreductase resolved to 1.65 Angstrom conta ins two domains: an N-terminal domain characteristic of a dinucleotide-bind ing 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 d omains such that the Si-faces of both face each other at a distance of 3.1 Angstrom, which is optimal for hydride transfer. Comparison of the structur es bound with and without substrates reveals that of the two substrates NAD P has to bind first, the binding being associated with an induced fit.