A large-conductance calcium-activated potassium channel in potato tuber mitochondria

Izabela Koszela-Piotrowska , Karolina Matkovic , Adam Szewczyk (1) , Wieslawa Jarmuszkiewicz

1 Laboratory of Intracellular Ion Channels

In the present study, we describe the existence of a novel potassium channel in the plant (potato 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 (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 α subunit and an auxiliary β2 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.

Mots clés: Life Sciences

Izabela Koszela-Piotrowska, Karolina Matkovic, Adam Szewczyk, Wieslawa Jarmuszkiewicz. A large-conductance calcium-activated potassium channel in potato tuber mitochondria. Biochemical Journal, 2009, 424 (2), pp.307-316. ⟨10.1042/BJ20090991⟩. ⟨hal-00479217⟩