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Oscillating Ca2+-induced channel activity obtained in BLM with a mitochondrial membrane component
G D Mironova1, A Lazareva, O Gateau-Roesch
1Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino.
Abstract:
Oscillations in ion fluxes and membrane potential may be observed in cells and in mitochondria as well. We obtained Ca2+-induced oscillations in channel activity in black-lipid membranes reconstituted with hydrophobic components extracted from mitochondria. Mitoplasts prepared from purified rat liver mitochondria were extracted with ethanol followed by Folch extraction and further partial purification by silicic acid chromatography. Channel activity was measured in lipid bilayers formed from bovine brain lipids and 10% cardiolipin with addition of the purified fractions. The conductance with 10 mM Ca2+ was 100 pS or its multiples. Ca2+ gradients of 4: 1 induced oscillating channel activity for several hours, with initial open states of 40 s and closed states of 56 s; the open times gradually decreasing to 8.6 s. No channel activity was seen without added fractions. The channel activity was associated with a Ca2+-binding lipid, nonpolar, low-molecular-weight fraction that in gel electrophoresis was not stained with Coomassie Blue and did not contain carbohydrate-staining material. 1H-Nuclear magnetic resonance spectra of the substance showed the presence of aliphatic chains and carbonyls, but the detailed structure remains to be elucidated.
Insights
Researchers discovered calcium-induced oscillations in mitochondrial channel activity. This finding sheds light on ion flux regulation and potential mechanisms in cellular energy production.
Area of Science:
- Biochemistry
- Cell Biology
- Mitochondrial Physiology
Background:
- Oscillations in ion fluxes and membrane potential are crucial in cellular functions.
- Mitochondria play a key role in cellular energy metabolism and calcium homeostasis.
Purpose of the Study:
- To investigate calcium-induced oscillations in channel activity using mitochondrial components.
- To identify the molecular basis of these oscillations in lipid bilayers.
Main Methods:
- Extraction and partial purification of hydrophobic mitochondrial components.
- Reconstitution of purified fractions into black-lipid membranes.
- Measurement of channel activity under calcium gradients using electrophysiology.
Main Results:
- Calcium gradients induced sustained oscillating channel activity in reconstituted lipid bilayers.
- The active component was a nonpolar, low-molecular-weight, calcium-binding lipid fraction.
- Spectroscopic analysis indicated aliphatic chains and carbonyl groups, but the exact structure is undetermined.
Conclusions:
- A specific lipid component from mitochondria mediates calcium-induced channel oscillations.
- These oscillations may play a role in regulating mitochondrial ion flux and cellular signaling.
- Further structural elucidation of the lipid is warranted to understand its precise function.