MethylH4MPTMtr

MethylH4MPTMtr refers to the methyltransferase complex that transfers a methyl group from methyl-tetrahydromethanopterin (methyl-H4MPT) to coenzyme M (CoM) in methanogenic archaea. The enzyme is commonly described as the Mtr (methyl-H4MPT:CoM methyltransferase) system and is encoded by a multi-gene operon, typically designated mtrA through mtrH, in various methanogens. The complex is membrane-associated and functions within the cytoplasmic membrane.

The primary reaction catalyzed by the methylH4MPTMtr system is methyl transfer: methyl-H4MPT + CoM-SH → H4MPT + methyl-CoM. The methyl group is temporarily carried by a corrinoid (cobalt-containing) cofactor, housed in the MtrA subunit, before it is transferred to CoM to form methyl-CoM. This transfer is coupled to the translocation of sodium ions across the membrane, a feature linked to energy conservation in methanogenesis.

Structurally, the Mtr complex comprises several subunits (commonly including A through H) that assemble at the membrane to coordinate methyl transfer and ion translocation. The activity of Mtr feeds into downstream steps of methane formation, as methyl-CoM is the substrate for methyl-coenzyme M reductase, which ultimately reduces CoM and CoB to methane.

MethylH4MPTMtr is found in diverse methanogenic archaea, including hydrogenotrophic and methylotrophic lineages. Its function is essential for linking the methyl branch of methanogenesis to cellular energy conservation and methane production.