title: Ion conductance pathways in potato tuber (Solanum tuberosum) inner mitochondrial membrane.
abstract: Single-ion channel activities were measured after reconstitution of potato tuber mitochondrial inner membranes into planar lipid bilayers. In addition to the recently described large-conductance Ca(2+)-activated potassium channel activity (Koszela-Piotrowska et al., 2009), the following mitochondrial ion conductance pathways were recorded: (i) an ATP-regulated potassium channel (mitoK(ATP) channel) activity with a conductance of 164+/-8pS, (ii) a large-conductance Ca(2+)-insensitive iberiotoxin-sensitive potassium channel activity with a conductance of 312 pS+/-23, and (iii) a chloride 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS)-inhibited channel activity with a conductance of 117 pS+/-4. In isolated non-phosphorylating potato tuber mitochondria, individual and combined potassium channel activities caused significant (up to 14mV) but not collapsing K(+)-influx-induced membrane potential depolarisation. Under phosphorylating conditions, the coupling parameters were unchanged in the presence of high K(+) level, indicating that plant K(+) channels function as energy-dissipating systems that are not able to divert energy from oxidative phosphorylation. A potato tuber K(+) channel that is ATP-, 5-hydroxydecanonic acid-, glybenclamide-inhibited and diazoxide-stimulated caused low cation flux, modestly decreasing membrane potential (up to a few mV) and increasing respiration in non-phosphorylating mitochondria. Immunological analysis with antibodies raised against the mammalian plasma membrane ATP-regulated K(+) channel identified a pore-forming subunit of the Kir-like family in potato tuber mitochondrial inner membrane. These results suggest that a mitoK(ATP) channel similar to that of mammalian mitochondria is present in potato tuber mitochondria.
authors.affiliation: Laboratory of Bioenergetics, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland.
authors.forename: Karolina
authors.initials: K
authors.lastname: Matkovic
authors.forename: Izabela
authors.initials: I
authors.lastname: Koszela-Piotrowska
authors.forename: Wieslawa
authors.initials: W
authors.lastname: Jarmuszkiewicz
authors.forename: Adam
authors.initials: A
authors.lastname: Szewczyk
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D004594:Electrophysiology; D015151:Immunoblotting; D015640:Ion Channel Gating / Q000187:drug effects; D008051:Lipid Bilayers / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects; D015221:Potassium Channels / Q000378:metabolism*; D011198:Solanum tuberosum / Q000187:drug effects / Q000378:metabolism*
chemical_list: D008051:Lipid Bilayers; D015221:Potassium Channels; C117780:mitochondrial K(ATP) channel; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid