This domain is found in a wide variety of proteins. These protein include potassium channels Swiss:P31069, phosphoesterases Swiss:Q59027, and various other transporters. This domain binds to NAD.

1: A novel family of predicted phosphoesterases includes Drosophila prune protein and bacterial RecJ exonuclease. Aravind L, Koonin EV; Trends Biochem Sci 1998;23:17-19. PMID:9478130

2: NAD+ binding to the Escherichia coli K(+)-uptake protein TrkA and sequence similarity between TrkA and domains of a family of dehydrogenases suggest a role for NAD+ in bacterial transport. Schlosser A, Hamann A, Bossemeyer D, Schneider E, Bakker EP; Mol Microbiol 1993;9:533-543. PMID:8412700

3: Regulatory potential, phyletic distribution and evolution of ancient, intracellular small-molecule-binding domains. Anantharaman V, Koonin EV, Aravind L; J Mol Biol 2001;307:1271-1292. PMID:11292341