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Phosphofructokinase: a component of the thick filament?
1Muscle Biology Division, AFRC Institute of Food Research-Bristol Laboratory, Langford, UK.
Advances in Experimental Medicine and Biology
|January 1, 1988
Summary
Phosphofructokinase (PFK), previously thought soluble, is identified as F-protein bound to muscle myofibrils. This key glycolytic enzyme is localized to the thick filament
Area of Science:
- Biochemistry
- Muscle Physiology
- Enzymology
Background:
- F-protein, a common contaminant in myosin preparations, has been identified.
- Phosphofructokinase (PFK) is the primary regulatory enzyme controlling glycolysis.
- Previous understanding suggested PFK existed in the soluble fraction of muscle cells.
Purpose of the Study:
- To identify the protein contaminant F-protein.
- To determine the cellular localization of phosphofructokinase (PFK) in muscle cells.
- To investigate the structural association of PFK with myofibrils.
Main Methods:
- Identification of F-protein as phosphofructokinase (PFK).
- Fractionation of muscle homogenates to analyze PFK distribution.
- Immunofluorescence microscopy using fluorescent antibodies against F-protein.
Main Results:
- PFK was found to sediment with myofibrils in rigor muscle homogenates, not in the soluble fraction.
- Fluorescent antibody labeling localized F-protein to specific zones within the A-band of myofibrils.
- The observed localization suggests PFK is associated with the cross-bridge regions of the thick filament.
Conclusions:
- Phosphofructokinase (PFK) is bound to myofibrils in living muscle cells, contrary to prior beliefs.
- PFK is likely located within the cross-bridge region of the thick filament.
- The accessibility of PFK to antibodies is modulated by the overlapping thin filaments.