NADP transhydrogenase, beta subunit (IPR012136)

Short name: NADH_DH_b

Overlapping homologous superfamilies


Family relationships



NAD(P) transhydrogenase catalyses the transfer of reducing equivalents between NAD(H) and NADP(H), coupled to the translocation of protons across a membrane [PMID: 12788487]. It is an integral membrane protein found in most organisms except for yeasts, plants and some bacterial species. In bacterial species it is located in the cytoplasmic membrane, while in mitochondria it is located in the inner membrane. Under most physiological conditions this enzyme synthesises NADPH, driven by consumption of the proton electrochemical gradient. The resulting NADPH is subsequently used for biosynthetic reactions or the reduction of glutathione.

The global structure of this enzyme is similar in all organisms, consisting of three distinct domains, though the polypeptide composition can vary. Domain I binds NAD(+)/NADH, domain II is a hydrophobic membrane-spanning domain, and domain III binds NADP(+)/NADPH. Domain I is composed of two subdomains, both of which form a Rossman fold, while domain III consists of a single Rossman fold where the NADP(+) is flipped relative to the normal orientation of bound nucleotides within the Rossman fold [PMID: 10997900, PMID: 11004437, PMID: 12791694]. Several residues within these domains are thought to make functionally important interdomain contacts for hydride transfer between these domains [PMID: 11250201]. Proton translocation occurs through domain II and is thought to induce conformational changes which are transmitted across domain III to the site of hydride transfer between domains I and III.

NAD(P) transhydrogenase from Escherichia coli contains an alpha subunit with the NAD(H)-binding domain I and a beta subunit with the NADP(H)-binding domain III. The membrane domain (domain II) harbors the proton channel and is made up of the hydrophobic parts of the alpha and beta subunits [PMID: 12974635]. This entry represents the beta subunit found in bacterial two-subunit NADP(H) transhydrogenases.

GO terms

Biological Process

GO:0055114 oxidation-reduction process

Molecular Function

GO:0008750 NAD(P)+ transhydrogenase (AB-specific) activity
GO:0050661 NADP binding

Cellular Component

GO:0016021 integral component of membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.