THE PRESENCE OF H-TRANSLOCATING ATPASES IN METHANOBACTERIUM-THERMOAUTOTROPHICUM AND THEIR POSSIBLE FUNCTION UNDER ALKALINE CONDITIONS( AND NA+)

Two ATPases with different apparent molecular masses of approx, 500 kD a and 400 kDa were identified in the EDTA extract of the cell membrane s of Methanobacterium thermoautotrophicum. Western blotting with polyc lonal antiserum reactive with beta-subunit of mitochondrial ATPase fro m rat liver and yeast was used for further analysis of these ATPases. A strong crossreactivity with a single protein band with an apparent m olecular weight of about 53 kDa (similar to beta-subunit of F-type ATP ase from other sources) was found in protein extracts of whole cells o f Methanobacterium thermoautotrophicum strains Delta H and Marburg, as well as of Methanospirillum hungatei. This indicates the presence of F-type ATPase in methanogens, ATP synthesis driven by membrane potenti al which was generated by artificially-imposed Delta pH in the presenc e of protonophorous uncoupler and sodium ions was stimulated by bafilo mycin A(1), an inhibitor of V- and A-type ATPases, as well as by harma line, an inhibitor of Na+/H+ antiporter. These results indicate that c ells of Methanobacterium thermoautotrophicum strain Delta H contain th e F-type ATP synthase which is Na+-translocating in addition to V- or A-type ATP synthase which is H+-translocating.