InterPro domain: IPR001750

Mrp-type antiporters comprise the cation/proton antiporter family 3 (CPA3), commonly referred to as Mrp. They are the products of operons that carry either six or seven genes (mrpA-G), and form complexes containing all subunits [ 1 , 2 ]. They have Na(+)/H(+) antiporter activity [ 3 ]. Two of the Mrp proteins, MrpA and MrpD, resemble NuoL/ND5, NuoM/ND4, NuoN/ND2, the homologous subunits that constitute the membrane-embedded, proton-translocating core of complex I [ 4 , 5 , 6 , 7 ]. They also resemble subunits of membrane-bound hydrogenases, such as HyfB, HyfD and HyfF from E.coli [ 8 ] and F420H2 dehydrogenasa (FPO complex) subunits L, N and M [ 9 ].

This domain is found in subunits NuoL/ND5, NuoM/ND4, and NuoN/ND2 of the NADH:quinone oxidoreductase (complex I), Mrp antiporters subunits A and D, and in membrane subunits of hydrogenase complexes, such as hydrogenase-4 and F420H2 dehydrogenase.

1. The Mrp system: a giant among monovalent cation/proton antiporters? Extremophiles 9, 345-54
2. Single gene deletions of mrpA to mrpG and mrpE point mutations affect activity of the Mrp Na+/H+ antiporter of alkaliphilic Bacillus and formation of hetero-oligomeric Mrp complexes. J. Bacteriol. 190, 4162-72
3. Purification and functional reconstitution of a seven-subunit mrp-type na+/h+ antiporter. J. Bacteriol. 196, 28-35
4. The 'antiporter module' of respiratory chain complex I includes the MrpC/NuoK subunit -- a revision of the modular evolution scheme. FEBS Lett. 549, 7-13
5. The membrane subunit NuoL(ND5) is involved in the indirect proton pumping mechanism of Escherichia coli complex I. J. Biol. Chem. 285, 39070-8
6. Transmembrane topology of the NuoL, M and N subunits of NADH:quinone oxidoreductase and their homologues among membrane-bound hydrogenases and bona fide antiporters. Biochim. Biophys. Acta 1556, 121-32
7. Functional modules and structural basis of conformational coupling in mitochondrial complex I. Science 329, 448-51
8. A 12-cistron Escherichia coli operon (hyf) encoding a putative proton-translocating formate hydrogenlyase system. Microbiology (Reading, Engl.) 143 ( Pt 11), 3633-47
9. The F420H2 dehydrogenase from Methanosarcina mazei is a Redox-driven proton pump closely related to NADH dehydrogenases. J. Biol. Chem. 275, 17968-73