Key result
Myosin's interacting head motif and super relaxed state may link via a molecular clutch.
Why the study?
The proposed connection between the myosin super relaxed state and the interacting head motif has been challenged and revised multiple times, leading to misunderstandings and improper assumptions.
This review clarifies the historical and current understanding of the relationship between the biochemical myosin super relaxed state and the structural interacting head motif in resting muscle.
Answers are grounded in this paper and cite their sources.
Informs myosin modulator therapies in HCM and HF; extends foundational SRX-IHM observations to resolve interpretive debates.
This short review acknowledges the scientific contribution of Roger Cooke and colleagues, who first introduced the idea of two different biochemical states in resting skeletal muscle thick filament. In a seminal paper published in 2010, the state defined as myosin “super relaxed state” (SRX) has been proposed as the biochemical counterpart of the structural motif named interacting head motif (IHM). This connection has been challenged and revised multiple times, leading to misunderstandings and improper assumptions. In this review, we discuss the recent history of the structure–biochemistry relationship associated with resting myosin thick filament, its current interpretation, and how this is possibly related to future myosin resting state studies.
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Nogara et al. (2026) conducted a review in Skeletal muscle resting state. The structural interacting head motif and the biochemical super relaxed state of myosin in resting skeletal muscle may be loosely tethered through a 'molecular clutch' mechanism rather than directly coupled.
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