A large-conductance calcium-activated potassium channel in potato (Solanum tuberosum) tuber mitochondria.
In the present study, we describe the existence of a novel potassium channel in the plant [potato (Solanum tuberosum) tuber] mitochondrial inner membrane. We found that substances known to modulate large-conductance calcium-activated potassium channel activity influenced the bioenergetics of potato tuber mitochondria. In isolated mitochondria, Ca2+ and NS1619 {1,3-dihydro-1-[2-hydroxy-5-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2H-ben-zimidazole-2-one; a potassium channel opener} were found to depolarize the mitochondrial membrane potential and to stimulate resting respiration. These effects were blocked by iberiotoxin (a potassium channel inhibitor) in a potassium-dependent manner. Additionally, the electrophysiological properties of the large-conductance potassium channel present in the potato tuber inner mitochondrial membrane are described in a reconstituted system, using planar lipid bilayers. After incorporation in 50/450 mM KCl gradient solutions, we recorded large-conductance potassium channel activity with conductance from 502+/-15 to 615+/-12 pS. The probability of channel opening was increased by Ca2+ and reduced by iberiotoxin. Immunological analysis with antibodies raised against the mammalian plasma-membrane large-conductance Ca2+-dependent K+ channel identified a pore-forming alpha subunit and an auxiliary beta2 subunit of the channel in potato tuber mitochondrial inner membrane. These results suggest that a large-conductance calcium-activated potassium channel similar to that of mammalian mitochondria is present in potato tuber mitochondria.
Koszela-Piotrowska
Izabela
I
Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur st., 02-093 Warsaw, Poland.
Matkovic
Karolina
K
Szewczyk
Adam
A
Jarmuszkiewicz
Wieslawa
W
D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D010940:Plant Proteins / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism*; D011198:Solanum tuberosum / Q000187:drug effects / Q000378:metabolism*
D051036:Large-Conductance Calcium-Activated Potassium Channels; D010455:Peptides; D010940:Plant Proteins; C064719:iberiotoxin