NAD-binding domains of dehydrogenases.

The nicotinamide adenine dinucleotide (NAD)-binding domains of dehydrogenases, containing a conserved double beta-alpha-beta-alpha-beta motif, are common structural feature of many enzymes that bind NAD, nicotinamide adenine dinucleotide phosphate (NADP) and related cofactors. Features of this folding pattern that create a natural binding site for such molecules have been described. The domain continues to appear in many structures, in the form of a common core with different peripheral additions or variations. Other structures that bind NAD and related molecules use entirely different topologies, although, in many, a phosphate group appears at the N terminus of an alpha helix. Ferredoxin reductase seems to show convergent evolution, containing a single beta-alpha-beta motif that is similar both in its structure and in its interactions with the ligand to a region in dehydrogenases.