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Visualization of mitochondrial coupling factor F1(ATPase) by freeze-drying
Cell Biophysics
|March 1, 1979
Summary
Submitochondrial particles (SMP) show F1 (ATPase) knobs on their surface, unlike freeze-etched membranes. Freeze-drying reveals these structures, confirming their presence on mitochondrial membranes.
Area of Science:
- Biochemistry
- Cell Biology
- Structural Biology
Background:
- Mitochondrial inner membranes contain F1 (ATPase) knobs.
- Previous freeze-etch studies suggested these knobs are absent from etched surfaces.
- Submitochondrial particles (SMP) are derived from the inner mitochondrial membrane.
Purpose of the Study:
- To investigate the presence of F1 (ATPase) knobs on submitochondrial particles (SMP).
- To reconcile conflicting observations from different electron microscopy techniques.
Main Methods:
- Transmission electron microscopy of freeze-dried SMP.
- Comparison with freeze-dried trypsin-urea treated (TU) particles, which lack F1 (ATPase).
- Analysis of negatively stained preparations.
Main Results:
- Freeze-dried SMP preparations clearly displayed the characteristic 9 nm F1 (ATPase) knobs.
- Freeze-dried TU particles, lacking F1 (ATPase), served as a control, showing no such knobs.
- These findings confirm the presence of F1 (ATPase) on the matrix side of the inner mitochondrial membrane.
Conclusions:
- The absence of F1 (ATPase) knobs in previous freeze-etch studies may be due to adsorbed water layers preventing sublimation.
- Freeze-drying is a suitable method for visualizing F1 (ATPase) on SMP.
- This study clarifies the structural organization of the mitochondrial ATP synthase complex.