Figure 5. Cross-bridge kinetic scheme relating muscle work production (process B) and work absorption (process C) to actomyosin cross-bridge cycle.

Figure 5

Cross-bridge kinetic scheme relating muscle work production (process B) and work absorption (process C) to actomyosin cross-bridge cycle. A is actin, M is myosin, T is ATP, D is ADP, and P is inorganic phosphate. The asterisk indicates a different conformational state. k±2 and k±4 are unidirectional rate constants, KP is the myosin phosphate affinity constant, KADP is the MgADP affinity constant, and KATP is the myosin MgATP affinity constant.31 The hatched box denotes weakly bound or detached states that cannot be distinguished on the basis of dynamic stiffness (complex modulus) measurements. The apparent rate constants of processes B and C are 2πb and 2πc, respectively. For b<<c (as in the example of Fig. 4), 2πb ˜[η k2/(η k2 +k-2)] k4 + ξ k-4, and 2πc ˜ ηk2 + k-2, where η = KATP[T] / (1 + KADP[D] + KATP[T]) and ξ = KP[P] / (1 + KP[P]).31

From: Insect Flight Muscle Chemomechanics

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