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The structural features of beef heart mitochondrial creatine kinase
L V Belousova1, S N Fedosov, E V Orlova
1Department of Biochemistry, School of Biology, M.V. Lomonosov State University, Moscow, USSR.
Biochemistry International
|May 1, 1991
Summary
Two forms of mitochondrial creatine kinase (Mi-CK) exist as distinct conformational states of an octameric molecule, not different oligomers. Structural analysis reveals an eight-subunit structure with high subunit mobility.
Area of Science:
- Biochemistry
- Structural Biology
- Mitochondrial Physiology
Background:
- Mitochondrial creatine kinase (Mi-CK) plays a crucial role in cellular energy buffering.
- Previous studies have identified different molecular weight forms of Mi-CK, but their structural relationship was unclear.
Purpose of the Study:
- To investigate the structural basis of the two observed forms of mitochondrial creatine kinase (Mi-CK).
- To determine if the different forms represent distinct oligomers or conformational states.
Main Methods:
- Gel-filtration chromatography (Sephacryl S-300) to determine molecular weight.
- Sedimentation coefficient analysis.
- Electron microscopy and image averaging to elucidate quaternary structure.
Main Results:
- Two forms of Mi-CK (320 kDa and 240 kDa) were identified with identical sedimentation coefficients.
- Electron microscopy revealed annular particles with eight subunits arranged around a central hollow.
- Structural mobility of subunits suggests the two forms are conformational states of an octameric molecule.
Conclusions:
- The 320 kDa and 240 kDa forms of Mi-CK are not different oligomers.
- These forms represent functionally distinct conformational states of the same octameric Mi-CK molecule.
- The octameric structure exhibits significant subunit lability and mobility.