The thin line between biochemistry and structure where myosin super relaxed state lies.

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.