Reduced coenzyme F420: heterodisulfide oxidoreductase, a proton- translocating redox system in methanogenic bacteria.

Abstract

Washed everted vesicles of the methanogenic bacterium strain Gol were found to couple the F42OH2-dependent heterodisulfide reduction with the transfer of protons across the membrane into the lumen of the everted vesicles. The transmembrane electrochemical potential of protons thereby generated was shown to be competent in driving ATP synthesis from ADP + Pi, exhibiting a stoichiometry of 2 H' translocated or 0.4 ATP synthesized per F42AH2 oxidized.This enzyme system exhibits the phenomenon of coupling and uncoupling and represents a different kind of electron transport chain with the heterodisulflde of 2-mercaptoethanesulfonate and 7-mercaptoheptanoylthreonine phosphate as terminal electron acceptor. The heterodisulfide and methane are formed in the methyl coenzyme M reductase reaction. The reducing equivalents are derived from reduced coenzyme F420, which represents an analogue of NADH + H' in other respiratory chains. It is assumed that the proton-translocating oxidoreductase discovered in strain Gol is of principal importance to all methanogenic bacteria not utilizing H2.With the discovery of methanogens and the elucidation of their specialized, strictly anaerobic metabolism, the question was posed whether this group of organisms gains ATP by substrate-level phosphorylation, such as clostridia or streptococci, or whether the process of methanogenesis is somehow coupled with the generation of a transmembrane gradient of protons (1). The pathways involved in methane formation from the few substrates utilized [C02 + H2, formate, methanol, methylamines, and acetate (2)] have been worked out

Effects of Nitrogen and Carbon Sources on Transcription of Soluble Methyltransferases in Methanosarcina mazei Strain Gö1

“…Cells were grown without shaking at 37°C in 5-or 50-ml closed growth tubes on 150 mM methanol and 40 mM acetate, which is defined as growth on methanol in the following or 25 mM trimethylamine (TMA) in a mineral medium under a nitrogen atmosphere containing 20% CO 2 as described previously (3,6). Nitrogen sufficiency (ϩNH 4 ϩ ) is defined as conditions under which 9 mM ammonium is added to an otherwise nitrogen-free medium, whereas nitrogen limitation (ϪNH 4 ϩ ) is defined in the following as conditions under which ammonium was omitted from the medium and molecular nitrogen in the gas atmosphere was the sole nitrogen source available.…”

Functional organization of a single nif cluster in the mesophilic archaeon Methanosarcina mazei strain Gö1

“…Methanosarcina mazei Gö1 was grown without shaking at 37°C, in 5-or 25-ml closed growth tubes on 150 mM methanol in a minimal medium described previously (Deppenmeier et al 1990). Growth generally took place in a nitrogen atmosphere containing 20% CO 2 .…”

“…This mesophilic archaeon belongs to the methylotrophic methanogens of the order Methanosarcinales and is able to grow on H 2 plus CO 2 , methanol, methylamines and acetate. The pathways of methanogenesis from these substrates have been analyzed in detail in recent years (Deppenmeier et al 1990, Thauer 1998, Ferry 1999) and the genome of M. mazei strain Gö1 has been sequenced by the Göttingen Genomics Laboratory (Deppenmeier et al 2002). Here we report on the arrangement and expression of nif genes in M. mazei.…”

N5-methyl-tetrahydromethanopterin:coenzyme M methyltransferase of Methanosarcina strain Gö1 is an Na(+)-translocating membrane protein

“…The location of the primary proton pump was identified (8), but the extrusion of Na+ could not be assigned to one single enzymatic reaction. However, it was shown that it is coupled to the conversion of formaldehyde (via methylene-tetrahydromethanopterin [H4MPT]) to the formal redox level of methanol, e.g., to methyl-coenzyme M (2-mercaptoethanesulfonate) (CoM-SH) (11,18).…”