Key Points
- To identify and characterize a protein fraction that sensitizes actomyosin to calcium-binding agents.
- Actin extracted from muscle was treated to prepare a protein fraction.
- Sedimentation and viscosity analyses were performed to assess the properties of the protein fraction.
- Amino acid analysis was conducted to compare the newly identified protein with tropomyosin.
- The protein fraction inhibited Mg++-activated ATPase activity in the absence of Ca++-binding agents.
- In the presence of the fraction, EGTA inhibited myosin ATPase activation by actin.
- Amino acid analysis indicated significant differences from tropomyosin, suggesting a new protein may be involved.
Structured PICO
PPopulationReconstituted actomyosin made with highly purified actin and myosin, and a protein fraction prepared from actin extracted from acetone-dried muscle powder at 25–37°
IInterventionEGTA-sensitizing protein fraction
CComparatorTropomyosin made by classical methods
OOutcomeMg++-activated adenosine triphosphatase (ATPase) activitysurrogate
A newly isolated tropomyosin-containing protein fraction sensitizes reconstituted actomyosin to calcium-binding agents, suggesting the presence of an additional protein regulating muscle contraction.