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Subunit exchange between smooth muscle myosin filaments.
1Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254.
Progress in Clinical and Biological Research
|January 1, 1987
Summary
Smooth muscle myosin filaments undergo extensive monomer exchange, challenging previous models. This explains why dephosphorylated myosin disassembles even with stable phosphorylated myosin present.
Area of Science:
- Biochemistry
- Molecular Biology
- Muscle Physiology
Background:
- Myosin filaments exist in equilibrium with a critical concentration of monomer.
- Previous models suggested limited monomer exchange, primarily at polymer ends.
Purpose of the Study:
- To investigate the extent of monomer exchange in smooth muscle myosin filaments.
- To explain the behavior of myosin copolymers with varying phosphorylation states.
Main Methods:
- Studies using smooth muscle myosin minifilaments and synthetic filaments.
- Observation of copolymer behavior in the presence of nucleotide (1 mM MgATP).
Main Results:
- Extensive monomer exchange occurs within myosin filaments, beyond just polymer ends.
- Dephosphorylated myosin disassembled to monomers upon MgATP addition, irrespective of stabilizing phosphorylated myosin.
Conclusions:
- Myosin monomer exchange is more dynamic than previously thought.
- Free exchange explains the lack of stabilization by phosphorylated myosin on dephosphorylated myosin within copolymers.