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Structural characterization of myosin from bovine brain
Abstract:
Myosins isolated from bovine brain, rabbit skeletal muscle, and chicken gizzard smooth muscle and their heavy meromyosin and light meromyosin fractions were studied in the electron microscope by negative staining with uranyl acetate. Under similar conditions of preparation and polymerization, the three myosins formed paracrystals of different structures. The light meromyosin portion of the skeletal muscle myosin also assembled in a different fashion than the brain or smooth muscle light meromyosins; the latter two assembled similarly. The heavy meromyosin portion from each of the three myosins was shown to interact with the actins isolated from each of the three tissue sources by the formation of the characteristic arrowhead patterns with similar periodicities. The brain heavy meromyosin attachment to both skeletal and brain actins was dissociated by ATP. It is suggested that differences in the light meromyosin portions of the three myosins may account in part for their differences in assembly in vivo.
Insights
Differences in light meromyosin (LMM) structures of myosins from various tissues influence their assembly. Heavy meromyosin (HMM) portions interact similarly with actin across different muscle types.
Area of Science:
- Biochemistry
- Cell Biology
- Structural Biology
Background:
- Myosins are crucial motor proteins involved in muscle contraction and cellular motility.
- Different myosin isoforms exist, varying in structure and function across diverse tissues.
Purpose of the Study:
- To investigate the structural differences and assembly properties of myosins from bovine brain, rabbit skeletal muscle, and chicken gizzard smooth muscle.
- To compare the assembly characteristics of heavy meromyosin (HMM) and light meromyosin (LMM) fractions from these myosins.
Main Methods:
- Electron microscopy with negative staining (uranyl acetate) was used to visualize myosin paracrystals.
- Myosin fractions (HMM and LMM) were isolated from different tissue sources.
- Interaction between HMM and actin was assessed by observing arrowhead patterns.
Main Results:
- Myosins from the three sources formed distinct paracrystal structures under similar preparation conditions.
- Skeletal muscle LMM assembled differently compared to brain and smooth muscle LMM, which assembled similarly.
- HMM from all three myosins interacted with respective actins, forming characteristic arrowhead patterns with consistent periodicity.
- ATP dissociated brain HMM binding to both skeletal and brain actins.
Conclusions:
- The distinct structural properties of LMM fractions likely contribute to the observed differences in myosin assembly in vivo.
- HMM portions exhibit conserved actin-binding capabilities across different myosin types.