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Uniquely stable 40 kDa subfragment-2 in carp myosin
Tomoko Tazawa Takahashi1, Masayuki Takahashi, Kunihiko Konno
1Laboratory of Marine Food Sciences, Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan.
Journal of Agricultural and Food Chemistry
|March 17, 2005
Summary
Calcium-dependent digestion of carp myofibrils yields heavy meromyosin (HMM). Further digestion produces a unique 40 kDa subfragment-2 (S-2), revealing insights into myosin rod stability.
Area of Science:
- Muscle protein biochemistry
- Structural biology of muscle contraction
Background:
- Myofibrils are the basic contractile units of muscle.
- Heavy meromyosin (HMM) is a key component involved in muscle contraction.
Purpose of the Study:
- To investigate the calcium-dependent digestion of carp myofibrils.
- To characterize the generated heavy meromyosin (HMM) and its subfragments.
Main Methods:
- Enzymatic digestion of carp myofibrils under varying temperature and ionic conditions.
- Isolation and characterization of heavy meromyosin (HMM) and subfragment-2 (S-2) using SDS-PAGE.
- N- and C-terminal sequencing for S-2 localization.
- Circular dichroism spectroscopy to determine thermal stability.
Main Results:
- Digestion at 30°C with calcium ions produced 135 kDa HMM, absent at 10°C.
- Further digestion of HMM yielded a 40 kDa S-2 fragment and S-1.
- The 40 kDa S-2 fragment, located at the amino end of the myosin rod, showed an unfolding temperature of ~52°C.
- Intact myosin rod exhibited unfolding peaks at ~52°C (40 kDa S-2) and ~36°C (light meromyosin).
- The 40 kDa S-2 fragment's stability was slightly reduced when part of the intact myosin structure.
Conclusions:
- Calcium ions and temperature critically influence HMM generation from myofibrils.
- A distinct 40 kDa S-2 fragment can be generated, providing a tool to study myosin rod structure.
- The head portion of myosin may contribute to the stability of the 40 kDa S-2 fragment.