Temperature sensitivity of the tonoplast Ca(2+)-activated K+ channel in Chara: the influence of reversing the sign of membrane potential.
A detailed temperature dependence study of a well-defined plant ion channel, the Ca(2+)-activated K+ channel of Chara corallina, was performed over the temperature range of their habitats, 5-36 degrees C, at 1 degree C resolution. The temperature dependence of the channel unitary conductance at 50 mV shows discontinuities at 15 and 30 degrees C. These temperatures limit the range within which ion diffusion is characterized by the lowest activation energy (Ea = 8.0 +/- 1.6 kJ/mol) as compared to the regions below 15 degrees C and above 30 degrees C. Upon reversing membrane voltage polarity from 50 to -50 mV the pattern of temperature dependence switched from discontinuous to linear with Ea = 13.6 +/- 0.5 kJ/mol. The temperature dependence of the effective number of open channels at 50 mV showed a decrease with increasing temperature, with a local minimum at 28 degrees C. The mean open time exhibited a similar behavior. Changing the sign of membrane potential from 50 to -50 mV abolished the minima in both temperature dependencies. These data are discussed in the light of higher order phase transitions of the Characean membrane lipids and corresponding change in the lipid-protein interaction, and their modulation by transmembrane voltage.
Djurisić
M R
MR
Institute of General and Physical Chemistry, Studentski trg 12-16/V, POB 551, 11001 Belgrade, Yugoslavia.
Andjus
P R
PR
D000460:Chlorophyta / Q000378:metabolism*; D015640:Ion Channel Gating / Q000502:physiology; D017136:Ion Transport; D007700:Kinetics; D008563:Membrane Lipids / Q000378:metabolism; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010940:Plant Proteins / Q000378:metabolism*; D018087:Plastids / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D013696:Temperature; D013816:Thermodynamics
D008563:Membrane Lipids; D008565:Membrane Proteins; D010940:Plant Proteins; D015221:Potassium Channels; D011188:Potassium