The interaction between myosin and actin filaments is regulated by:
Coordinated muscle contraction depends on interplay between chemical fuel and regulatory ion signals ensuring contraction only when needed. ATP provides both detach signal and energy currency: ATP binding to myosin head after power stroke dissociates rigor cross bridge, while its hydrolysis to ADP Pi stores elastic energy in lever arm for next stroke, and Pi plus ADP release execute mechanical work. Without ATP muscle enters rigor state as observed in cadaveric stiffness. Calcium provides temporal switch: at rest sarcoplasmic reticulum SERCA maintains cytosolic calcium about 100 nM insufficien
Ref: Gordon et al., Physiol Rev 2000; Alberts Chapter 16 – Regulation of actin-myosin by ATP and Ca2+ availability.
