Channel-forming activities of peroxisomal membrane proteins from the yeast Saccharomyces cerevisiae.
Highly-purified peroxisomes from the yeast Saccharomyces cerevisiae grown on oleic acid were investigated for the presence of channel (pore)-forming proteins in the membrane of these organelles. Solubilized membrane proteins were reconstituted in planar lipid bilayers and their pore-forming activity was studied by means of multiple-channel monitoring or single-channel analysis. Two abundant pore-forming activities were detected with an average conductance of 0.2 and 0.6 nS in 1.0 m KCl, respectively. The high-conductance pore (0.6 nS in 1.0 m KCl) is slightly selective to cations (P(K+)/P(Cl-) approximately 1.3) and showed an unusual flickering at elevated (> +/-40 mV) holding potentials directed upward relative to the open state of the channel. The data obtained for the properties of the low-conductance pore (0.2 nS in 1.0 m KCl) support the notion that the high-conductance channel represents a cluster of two low-conductance pores. The results lead to conclusion that the yeast peroxisomes contain membrane pore-forming proteins that may aid the transfer of small solutes between the peroxisomal lumen and cytoplasm.
Grunau
Silke
S
Institut für Physiologische Chemie, Abt. Systembiochemie, Bochum, Germany.
Mindthoff
Sabrina
S
Rottensteiner
Hanspeter
H
Sormunen
Raija T
RT
Hiltunen
J Kalervo
JK
Erdmann
Ralf
R
Antonenkov
Vasily D
VD
D004591:Electrophoresis, Polyacrylamide Gel; D007473:Ion Channels / Q000378:metabolism*; D008051:Lipid Bilayers; D046529:Microscopy, Electron, Transmission; D020675:Peroxisomes / Q000201:enzymology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
D007473:Ion Channels; D008051:Lipid Bilayers; D029701:Saccharomyces cerevisiae Proteins