NAD(P) transhydrogenase  (PTH) catalyzes the conversion of NADP and NADH to NADPH and NAD.  The reaction is coupled with proton translocation across the cell membrane while the enzyme undergoes conformational change.  PTH uses FAD as cofactor.  PTH is composed of 3 domains.:
-  Domain I binds NAD(+)/NADH.
 -  Domain II is a membrane-spanning domain.
 -  Domain III binds NADP(+)/NADPH.
 
PTH is composed of 2 subunits.  Subunit beta contains domain III and part of II.
 3D structures of NAD(P) transhydrogenase
Updated on 01-December-2014
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- NAD(P) transhydrogenase domain I===
 
1l7d – RrPTH domain I – Rhodospirillum rubrum 
1l7e – RrPTH domain I + NAD 
1x13 – EcPTH domain I – Escherichia coli 
1x14, 1x15 – EcPTH domain I + NAD 
4dio – PTH domain I – Sinorhizobium meliloti
 PTHNAD(P) transhydrogenase domain III
1e3t – RrPTH domain III + NADP - NMR
1pno – RrPTH domain III + NADP 
1pnq – RrPTH domain III + NADPH 
1d4o – bPTH domain III + NADP - bovine
1djl, 1u31 – hPTH domain III + NADP - human
1pt9 – hPTH domain III + NADP analog
 PTHNAD(P) transhydrogenase domain I+III
1hzz, 1u28, 1u2d, 1xlt – RrPTH domain I+III + NADP + NAD
1f8g – RrPTH domain I+III + NAD
1nm5, 2fr8, 2fsv – RrPTH domain I+III (mutant) + NADP + NAD
1ptj, 1u2g, 2frd, 2oo5 – RrPTH domain I+III + NADP + NAD derivative
2oor – RrPTH domain I+III + NADP derivative + NAD
2bru – EcPTH domain I+III + NADP + NAD - NMR
4j16, 4j1t – PTH domain I+III + NADP + NAD – Thermus thermophilus