CONDITIONS ALLOWING DIFFERENT STATES OF ATP-INDUCED AND GDP-INDUCED PERMEABILITY IN MITOCHONDRIA FROM DIFFERENT STRAINS OF SACCHAROMYCES-CEREVISIAE

The effect of ATP and other nucleotides on the respiration of Saccharo myces cerevisiae mitochondria was investigated. It was observed that A TP induced a stimulation of the respiration rate only in the presence of a salt in mitochondria from the baker's yeast Yeast Foam, whereas a n ATP-induced stimulation occurred even in the absence of salt in mito chondria from three different laboratory strains. In both cases, the s timulation was related to a collapse of the transmembrane potential, s uggesting the opening of ion- and/or proton-conducting pathways. Not o nly ATP, but also GTP and CTP, induced these pathways. Moreover, a sim ilar stimulation was obtained with GDP and its analog GDP-beta-S. The fact that, as opposed to NTPs, GDP did not induce any non-specific ani on channel, allowed us to use it to demonstrate unambiguously that a p roton-conducting pathway was opened through the inner mitochondrial me mbrane of laboratory strains but not of Yeast Foam. Three additional a spects of this nucleotide-induced permeability were investigated. (i) The proton-conducting pathway was insensitive to Mg2+, whereas the ani on-conducting pathway was fully inhibited by 4 mM Mg2+. (ii) The proto n-conducting pathway of mitochondria isolated from laboratory strains was opened by the action of nucleotides outside the mitochondrion, sin ce it was fully insensitive to (carboxy)atractyloside, and fully activ e in mitochondria isolated from op1 and Delta anc strains. On the othe r hand, the cation-conducting pathway of Yeast Foam mitochondria was p artly sensitive to (carboxy)atractyloside and insensitive to bongkreki c acid, suggesting a role of the conformational state of ANC in this a ctivity. (iii) Both the proton and cation-conducting pathways were inh ibited by very low concentrations of vanadate, under conditions where this oxyanion was polymerized to decavanadate, a competitor to nucleot ide-binding sites on some enzymes.