A review of the binding-change mechanism for proton-translocating transhydrogenase

► Transhydrogenase couples the reduction of NADP+ by NADH to proton translocation. ► Coupling is probably achieved by a binding-change mechanism. ► Protonation/deprotonation interconverts the enzyme between open and occluded states. ► Nucleotide binding, proton access and hydride transfer are switched during catalysis. ► Experimental evidence for the binding-change mechanism is reviewed.