ABSTRACT
Coenzyme M (2-mercaptoethane sulfonic acid) and factor F430 (a nickel porphinoid) are coenzymes found in methanogenic bacteria. Recently it has been proposed that in these bacteria a coenzyme MF430 also exists which plays a key role in methane formation and in which coenzyme M and F430 are bound to each other. To test this hypothesis Methanobrevibacter ruminantium, which requires coenzyme M as a vitamin, was grown in the presence of [2-14C]CoMSH. F430 and 'CoM' (mixture of CoMSH and its disulfides) were quantitatively extracted from these cells and from partially purified methyl-CoM reductase using various methods. The extracts were chromatographed on cellulose or Sephadex G-10. Under all conditions factor F430 and 'CoM' were completely (greater than 99%) separated. There was no indication for the existence of a protein-free F430 species containing covalently bound coenzyme M in Mb. ruminantium. The results support the structure previously assigned to coenzyme F430.
Subject(s)
Euryarchaeota/metabolism , Mercaptoethanol/analogs & derivatives , Mesna/metabolism , Metalloporphyrins , Metalloproteins/metabolism , Nickel/metabolism , Binding Sites , Chemical Phenomena , Chemistry , Chromatography, Gel , Chromatography, Ion Exchange , Euryarchaeota/enzymology , Mesna/isolation & purification , Metalloproteins/isolation & purification , Nickel/isolation & purification , Oxidoreductases/isolation & purification , Oxidoreductases/metabolism , TemperatureABSTRACT
Factors F430 from methanogenic bacteria have recently been shown to contain nickel and it has been speculated that they may have a nickel tetrapyrrole structure. This assumption was tested by determining whether succinate is incorporated by growing Methanobacterium thermoautotrophicum into three factors F430. Succinate is assimilated by Methanobacterium thermoautotrophicum into the amino acids glutamate, arginine and proline and into tetrapyrroles rather than other cell components. It was found that per mol nickel 8--9 mol of succinate were incorporated into the three factors F430 which is the amount predicted for a tetrapyrrole structure. Since the three factors F430 only contained significant amounts of glutamate rather than arginine or proline, the incorporation data suggest that factors F430 are nickel tetrapyrrole compounds. Spectral properties of the three factors F430, apparent molecular weights, and the absence of phosphor in these compounds are also described.
