A study of the Na+/H+ antiport in the archaeon Methanobacterium thermoautotrophicum strain delta H.
The ability of the cells of Mb. thermoautotrophicum strain delta H to generate a proton gradient (driven by a concentration gradient of sodium ions) at pH 6.8 as well as at pH 8 was demonstrated. The electrogenic Na+/H+ antiport responsible for this process was shown to be inhibited by EIPA and also by DCCD. Artificially increasing of intracellular concentration of Ca2+ in these cells enhanced the Na+/H+ antiport activity, while the lowering of external Ca2+ by EGTA significantly decreased this activity. The apparent K(m) values for Na+ about 14 and 3 mM at pH 6.8 and 8, respectively, and Vmax about 214 (pH 6.8) and 155 (pH 8) delta Q/min per mg of cell proteins, respectively, were calculated. It is concluded that the described processes are mediated by the Na+/H+ antiporter which might be a clue to the adaptive bioenergetic behaviour of the cells of Mb. thermoautotrophicum strain delta H under the different physiological conditions.
Majerník
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A
Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences, Ivanka pri Dunaji, Slovak Republic. majernik@ubgz.savba.sk
Smigán
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P
Greksák
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M
D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008564:Membrane Potentials; D017014:Methanobacterium / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013696:Temperature
D017923:Sodium-Hydrogen Exchangers; D004533:Egtazic Acid; D004024:Dicyclohexylcarbodiimide; D000584:Amiloride; D006859:Hydrogen; D012964:Sodium; D008274:Magnesium; D002118:Calcium; C039614:ethylisopropylamiloride