Axial and Radial Forces of Cross-Bridges Depend on Lattice Spacing
Figure 1
Cross-bridge types and kinetic scheme.
(A)–(C) The three cross-bridge models, plotted against a myosin crystal structure for comparison (structure image generated from Gourinath et al. (2003) [40] with PyMol [41]). The energy landscape of each cross-bridge and the free energy at rest lattice spacing are shown adjacent to the cross-bridge schematic. (A) The 1sXB introduced in Huxley (1957) [11]. (B) The 2sXB which uses a torsional/angular spring () and an extensional spring (
). (C) The 4sXB with two torsional and two extensional springs. Of the 4sXB's springs,
corresponds to the point at which the S2 region rejoins the thick filament backbone,
to the S2 region itself,
to the area linking the S2 and the light chain domains, and
to the light chain domain itself.
replicates the change in angle accompanying the power stroke by applying torque to the freely moving joint representing the converter domain. (D) The three state kinetic system. The three states represent (1) an unbound state, (2) a pre-power stroke state, and (3) a post-power stroke state. The rate of transition between states
and
is represented as
. The forward and reverse transition rate constants are functions of energy stored in the cross-bridge.