Poorly Understood Aspects of Striated Muscle Contraction

Table 1

Conflicting evidence from experimental studies and theoretical considerations related to temporal relationship between P_i release and force-generating step in actomyosin cross-bridge cycle in muscle.

Force-gen. before Pi release	Pi release before force-gen.	Loose coupling
Kawai and Halvorson [89]; Pi release fast	Davis and Epstein [230]. L-jumps and T-jumps in skinned muscle fibers	Caremani et al. [122]. Load-clamp expts. in skinned muscle fibers at varied [Pi]
Dantzig et al. [233] based on Pi jump experiments in skinned muscle fibers; Pi release fast	Davis and Rodgers [229]
Tesi et al. [235] Pi-jumps and tension versus [Pi] in myofibrils; Pi release fast	Spudich [16]
Smith and Sleep [324] based on comparison of kinetic models; Pi release slow	Sweeney and Houdusse [60] from reviewing structural data from several studies
Ranatunga [209] from reviewing own work and work by others; Pi release fast	Conibear et al. [359]
Caremani et al. [236]. Contraction of skinned fibres at different [Pi]; Pi release fast
Muretta et al. [323]. Spectroscopy applied to Dictyostelium myosin II; Pi release slow