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 |
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Authors: | Pérez-Vázquez Victoriano Saavedra-Molina Alfredo Uribe Salvador |
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Institution: | (1) Instituto de Fisiología Celular, UNAM, México, DF, México;(2) Instituto de Investigaciones Químico-Biológicas UMSNH, México, DF, México |
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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 (![Delta](/content/g24772n847961035/xxlarge916.gif) ), 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 M) was the only cation which inhibited mitochondrial recontraction, probably as a result of membrane binding stabilization through its hydrophobic tail. The PO4-dependent, Ca2+/Mg2+-mediated closure of the YMUC may be a means to control the proportion of oxidative energy producing ATP or being lost as heat. |
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Keywords: | Ca2+ Mg2+ octyl-guanidine permeability transition phosphate energetic charge YMUC |
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