cross-bridge (XB)

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cross-bridge (XB)

in full (actin-)myosin cross-bridge in muscle, strictly refers to the molecular structure consisting of a myosin head-group bound to an actin molecule. Widely, though loosely, also used for the head-group alone, particularly when seen as an ultrastructural component in a striated muscle fibre. cross-bridge cycle cycle of force-generating attachment/detachment interactions between myosin head-groups and actin, powered by the hydrolysis of ATP. See also length-tension relationship, muscle contraction, myosin; appendix 1.2 .