title: In Saccharomyces cerevisiae, cations control the fate of the energy derived from oxidative metabolism through the opening and closing of the yeast mitochondrial unselective channel.
abstract: The yeast mitochondrial unspecific channel (YMUC) sensitivity to inorganic (Ca2+ or Mg2+) or organic (hexyl or octyl-guanidine) cations was measured. The rate of oxygen consumption in State 3 and State 4, the transmembrane potential (deltapsi), mitochondrial swelling, and the polyethylene-glycol mediated recontraction were used to follow opening of the YMUC. Addition of 0.4 mM PO4 did not close the YMUC, although it did enhance the sensitivity to Ca2+ (I50 decreased from 50 to 0.3 mM) and Mg2+ (I50 decreased from 5 to 0.83 mM Mg2+). The Ca2+ concentration needed to close the YMUC was higher than the concentrations usually observed in the cell. Nonetheless, Mg2+, Ca2+, and PO4 exhibited additive effects. These cations did not inhibit contraction of preswollen mitochondria, suggesting that the YMUC/cation interaction was labile. Octyl-guanidine (OG-I50 7.5 microM) was the only cation which inhibited mitochondrial recontraction, probably as a result of membrane binding stabilization through its hydrophobic tail. The PO4-dependent, Ca(2+)/Mg(2+)-mediated closure of the YMUC may be a means to control the proportion of oxidative energy producing ATP or being lost as heat.
mesh_terms: D002118:Calcium / Q000494:pharmacology; D002412:Cations; D004734:Energy Metabolism; D004735:Energy Transfer; D006146:Guanidines / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008564:Membrane Potentials; D024101:Mitochondrial Proteins / Q000378:metabolism / Q000502:physiology*; D008933:Mitochondrial Swelling; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010710:Phosphates / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000502:physiology*
chemical_list: D002412:Cations; D006146:Guanidines; D024101:Mitochondrial Proteins; D010710:Phosphates; D015221:Potassium Channels; D029701:Saccharomyces cerevisiae Proteins; C477372:YMUC potassium channel protein, S cerevisiae; C015403:octylguanidine; D008274:Magnesium; D002118:Calcium