Energetic process of muscle contraction.

Muscle contraction takes place by relative sliding of myosin-containing thick filament and actin-containing thin filament. The mechanical energy of sliding is supplied from the chemical energy of ATP hydrolysed by the actomyosin system, and the chemomechanical energy transformation in contracting muscle is highly efficient. As crossbridges which extrude from thick filaments can bind with thin filaments and hydrolyse ATP, the secret of the chemomechanical energy transformation must reside in the specific way of molecular interaction between ATP-hydrolysing crossbridges and thin filaments. However, detailed molecular mechanism of the energy transfer process (and also that of the force generation process itself) has not been clarified. Only very recently several experimental results have been obtained which may be directly related with the energetic process associated with the elementary ATP splitting cycle in contracting muscle. In this review we will see the classical view of energetic process of muscle contraction, later experimental results which required the revision of the classical view, and then recent experimental approaches.