The methyl-tetrahydromethanopterin: Coenzyme M methyltransferase of Methanosarcina strain Gö1 is a primary sodium pump

Abstract

Washed inverted vesicle preparations of Methanosarcina strain Gö1 catalyzed the formation of methyl-CoM from formaldehyde, H2 and CoM in the presence of tetrahydromethanopterin and 2-bromoethanesulfonate. The reaction was associated with the translocation of sodium ions into the lumen of the vesicles. This translocation was abolished by the Na+ ionophore ETH 157 but it was insensitive to the addition of the uncoupler SF6847 and the Na+/H+ antiport inhibitor amiloride and, therefore, is the result of a primary Na+ pump. Since the translocation of Na+ was also observed when formaldehyde + tetrahydromethanopterin was replaced by methyl-tetrahydromethanopterin, it follows that the methyl transfer from tetrahydromethanopterin to CoM is the sodium-motive reaction. Methyl-tetrahydromethanopterin could be replaced by methyl-tetrahydrofolate.