DELTA-MU(NA-MU(NA+)-TRANSLOCATING F1F0-ATP SYNTHASE IN MEMBRANE-VESICLES OF THE ARCHAEON METHANOSARCINA-MAZEI GO1() DRIVES THE SYNTHESIS OFATP VIA AN DELTA)

Methanosarcina mazei Go1 couples the methyl transfer from methyl-tetra hydromethanopterin to 2-mercaptoethanesulfonate (coenzyme M) with the generation of an electrochemical sodium ion gradient (Delta mu(Na)+) a nd the reduction of the heterodisulfide of coenzyme M and 7-mercaptohe ptanoylthreoninephosphate with the generation of an electrochemical pr oton gradient (Delta mu(H)+). Experiments with washed inverted vesicle s were performed to investigate whether both ion gradients are used di rectly for the synthesis of ATP. Delta mu(Na)+ and Delta mu(H)+ were b oth able to drive the synthesis of IITP in the vesicular system. ATP s ynthesis driven by heterodisulfide reduction (Delta mu(H)+) or an arti ficial Delta pH was inhibited by the protonophore SF6847 but not by th e sodium ionophore ETH157, whereas ETH157 but not SF6847 inhibited ATP synthesis driven by a chemical sodium ion gradient (Delta p(Na)) as w ell as the methyl transfer reaction (Delta mu(Na)+) Inhibition of the Na+/H' antiporter led to a stimulation of ATP synthesis driven by the methyl transfer reaction (Delta mu(Na)+), as well as by Delta p(Na). T hese experiments indicate that Delta mu(Na)+ and Delta mu(H)+ drive th e synthesis of ATP via an Na+- and an H+-translocating ATP synthase, r espectively. Inhibitor studies were performed to elucidate the nature of the ATP synthase(s) involved. Delta pH-driven ATP synthesis was spe cifically inhibited by bafilomycin A(1), whereas Delta pNa-driven ATP synthesis was exclusively inhibited by 7-chloro-4-nitro-2-oxa-1,3-diaz ole, azide, and venturicidin. These results are evidence for the prese nce of an F1F0-ATP synthase in addition to the A(1)A(0)-ATP synthase i n membranes of M. mazei G61 and suggest that the F1F0-type enzyme is a n Na+-translocating ATP synthase, whereas the A(1)A(0)-ATP synthase us es H+ as the coupling ion.