Force production by chemically crosslinked myosin-actin crossbridges in rabbit skinned fibers in response to MgATP depletion.

In order to study the contractile property of myosin crossbridges attached to thin filaments, myosin heads were crosslinked to the filaments at their interface in single skinned rabbit psoas fibers with a zero-length chemical crosslinker, 1-(3-dimethylamino-propyl)-3-ethylcarbodiimide (EDC). The results obtained show that a partially crosslinked single fiber produces a large rigor-like force when MgATP is depleted from the myofibrillar space. Such crosslinked fibers contain two types of crosslinked myosin heads: one with one of the two heads of the myosin molecule crosslinked to actin with the other head uncrosslinked; the other has both heads crosslinked to actin. The results of this work suggest that a crosslinked myosin head of the former type produces a much larger force than the latter type.