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Molluscan twitchin can control actin-myosin interaction during ATPase cycle
Yurii S Borovikov1, Nikolay S Shelud'ko, Stanislava V Avrova
1Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia. boroviko@mail.cytspb.rssi.ru
Archives of Biochemistry and Biophysics
|January 12, 2010
Summary
Twitchin protein regulates muscle contraction by modulating actin-myosin interactions. Phosphorylation of twitchin controls its inhibitory effect on muscle power, revealing a novel regulatory mechanism.
Area of Science:
- Muscle Physiology
- Biochemistry
- Molecular Biology
Background:
- Twitchin is a thick filament protein in molluscan muscles.
- Actin-myosin interaction is central to muscle contraction and the ATPase cycle.
Purpose of the Study:
- To investigate the effect of twitchin on actin-myosin interaction during the ATPase cycle.
- To elucidate the role of twitchin phosphorylation in regulating muscle contraction.
Main Methods:
- Utilized fluorescent probes targeting specific cysteine residues on myosin subfragment-1 and actin.
- Employed ghost muscle fibers to mimic in vivo conditions.
- Monitored changes in protein mobility and spatial arrangement during the ATPase cycle.
Main Results:
- Demonstrated that unphosphorylated twitchin inhibits the movement of myosin SH1 helix and actin subdomain-1.
- Showed a decrease in myosin head and actin affinity in the presence of unphosphorylated twitchin.
- Confirmed that phosphorylation of twitchin by protein kinase A reverses these inhibitory effects.
Conclusions:
- Twitchin regulates actin-myosin interaction in a phosphorylation-dependent manner.
- Twitchin inhibits the transition from weak-binding to strong-binding actomyosin states during the ATPase cycle.
- Identified a novel mechanism for twitchin in controlling muscle contraction dynamics.
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