Key result
Heating myosin filaments progressively reduces thickness and induces strand formation at higher temperatures.
Why the study?
Heat-induced morphological changes in myosin filaments were not well characterized at different temperatures.
Thermal treatment of myosin filaments induces progressive structural changes and aggregation into strands, as visualized by atomic force microscopy.
May inform food heating protocols; extends in vitro myosin aggregation data but leaves open cardiac muscle relevance.
Heat-induced morphological change in myosin filaments was observed using atomic force microscope. The thickness of fixed native myosin filament was estimated to be 95 +/- 5 nm. When myosin filaments in 0.1 M NaCl at pH 6.0 were heated at 40, 55, and 70 degrees C for 10 min, the particulate structure appeared spirally on the surface of the filament at 40 degrees C, and the thickness of the filament was 75 +/- 10 nm. When myosin filaments were treated at 55 degrees C, several filaments were formed associated with side-by-side interaction through projected myosin heads to form a strand. The surface of the strand looked knobby. The thickness of thermally denatured filaments at 55 degrees C was 48 +/- 5 nm, and that of strands was about 80-110 nm, indicating the involvement of several filaments in a strand. The strands became to be rope-like at 70 degrees C, and the individual filaments in a strand were not distinguishable.
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Iwasaki et al. (2005) studied this question. Thermal treatment vs. Native myosin filament was evaluated on Morphological change and thickness of myosin filaments. Thermal treatment of myosin filaments at 40, 55, and 70 degrees C induced progressive morphological changes, reducing filament thickness and causing side-by-side strand formation at higher temperatures.
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