Dissecting cooperative calmodulin binding to CaM kinase II: a detailed stochastic model
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- Byrne, M.J., Putkey, J.A., Neal Waxham, M. et al. J Comput Neurosci (2009) 27: 621. doi:10.1007/s10827-009-0173-3
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Calmodulin (CaM) is a major Ca2+ binding protein involved in two opposing processes of synaptic plasticity of CA1 pyramidal neurons: long-term potentiation (LTP) and depression (LTD). The N- and C-terminal lobes of CaM bind to its target separately but cooperatively and introduce complex dynamics that cannot be well understood by experimental measurement. Using a detailed stochastic model constructed upon experimental data, we have studied the interaction between CaM and Ca2+-CaM-dependent protein kinase II (CaMKII), a key enzyme underlying LTP. The model suggests that the accelerated binding of one lobe of CaM to CaMKII, when the opposing lobe is already bound to CaMKII, is a critical determinant of the cooperative interaction between Ca2+, CaM, and CaMKII. The model indicates that the target-bound Ca2+ free N-lobe has an extended lifetime and may regulate the Ca2+ response of CaMKII during LTP induction. The model also reveals multiple kinetic pathways which have not been previously predicted for CaM-dissociation from CaMKII.