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Metal cation controls myosin and actomyosin kinetics
Yaroslav V Tkachev1, Jinghua Ge, Igor V Negrashov
1Department of Physics and Optical Science, University of North Carolina, Charlotte, North Carolina, 28223; Engelhardt Institute of Molecular Biology RAS, Moscow, 119991, Russia.
Protein Science : a Publication of the Protein Society
|October 12, 2013
Summary
Metal cations influence myosin ATPase rate-limiting steps and recovery stroke speeds, but not actin activation. Nucleotide release and ATP binding depend on cation coordination number.
Area of Science:
- Biochemistry
- Molecular Biology
- Muscle Physiology
Background:
- Myosin ATPase activity is central to muscle contraction.
- Understanding the role of metal cations in myosin function is crucial.
- Previous studies have characterized Dictyostelium discoideum myosin constructs.
Purpose of the Study:
- To investigate the role of metal cations (magnesium, manganese, calcium) in myosin ATPase pathways.
- To probe the influence of cation properties on nucleotide binding, dissociation, and ATP hydrolysis in the presence of actin.
- To elucidate the rate-limiting steps and mechanical transitions during the myosin ATPase cycle.
Main Methods:
- Utilized transient time-resolved Förster Resonance Energy Transfer (FRET).
- Measured myosin intrinsic fluorescence and fluorescence of pyrene-labeled actin.
- Performed steady-state myosin ATPase activity assays on a specific Dictyostelium discoideum myosin construct (A639C:K498C).
Main Results:
- Actin activation of myosin ATPase is independent of the specific metal cation used.
- The rate-limiting step of myosin ATPase is dependent on the type of metal cation.
- The rates of the recovery stroke and reverse recovery stroke correlate with the cation's ionic radius.
- Nucleotide release from myosin and actomyosin, and ATP binding to actomyosin, are influenced by the cation's coordination number.
Conclusions:
- Metal cation identity significantly impacts the kinetics of the myosin ATPase cycle, particularly the rate-limiting step and mechanical transitions.
- While actin activation is cation-independent, specific cation properties like ionic radius and coordination number dictate crucial steps in ATP hydrolysis and nucleotide exchange.
- These findings provide detailed insights into the mechanistic pathways of myosin ATPase and the role of metal ions in regulating muscle function.
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