C. Ballarin et Mc. Sorgato, AN ELECTROPHYSIOLOGICAL STUDY OF YEAST MITOCHONDRIA - EVIDENCE FOR 2 INNER MEMBRANE ANION CHANNELS SENSITIVE TO ATP, The Journal of biological chemistry, 270(33), 1995, pp. 19262-19268
The inner membrane of mitochondria from various strains of Saccharomyc
es cerevisiae has been analyzed with the patch clamp technique for com
parison with the better known homologous membrane in mammals (Sorgato,
M. C., and Moran, O. (1993) CRC Grit. Rev. Biochem. Mol. Biol. 18, 12
7-171). Differently than in mammals, the yeast inner membrane was foun
d to harbor essentially two channels with similar anionic selectivity
but otherwise different functional behavior. One had a conductance of
around 45 picosiemens (in symmetrical 150 mM KCl) and an activity only
marginally sensitive to voltage. The other channel was prominent for
the higher outwardly rectifying current and for the dependence upon vo
ltage of the open probability that induced rapid closure at physiologi
cal (negative) membrane potentials. Particularly interesting was the e
ffect of ATP (Mg2+ free) added on the matrix side of the membrane, In
the case of the lower conducting channel, the nucleotide caused an imm
ediate block of activity (IC50, 0.240 mM), whereas it locked the large
r conductance in the open state at both positive and negative potentia
ls, In proteoliposomes containing both mitochondrial membranes, the sm
all conductance was clearly evident, whereas a larger channel, cationi
c and without the voltage dependence typical of that in the native inn
er membrane, was found.