The Hill Model for Binding Myosin S1 to Regulated Actin Is not Equivalent to the McKillop–Geeves Model

Mijailovich, Srboljub M. and Li, Xiaochuan and Griffiths, R. Hugh and Geeves, Michael A. (2012) The Hill Model for Binding Myosin S1 to Regulated Actin Is not Equivalent to the McKillop–Geeves Model. Journal of Molecular Biology, 417 (1-2). pp. 112-128. ISSN 0022-2836. (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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The Hill two-state cooperativity model and the McKillop–Geeves (McK–G) three-state model predict very similar binding traces of myosin subfragment 1 (S1) binding to regulated actin filaments in the presence and absence of calcium, and both fit the experimental data reasonably well [Chen et al., Biophys. J., 80, 2338–2349]. Here, we compared the Hill model and the McK–G model for binding myosin S1 to regulated actin against three sets of experimental data: the titration of regulated actin with S1 and the kinetics of S1 binding of regulated actin with either excess S1 to actin or excess actin to S1. Each data set was collected for a wide range of specified calcium concentrations. Both models were able to generate reasonable fits to the time course data and to titration data. The McK–G model can fit all three data sets with the same calcium-concentration-sensitive parameters. Only KB and KT show significant calcium dependence, and the parameters have a classic pCa curve. A unique set of the Hill model parameters was extremely difficult to estimate from the best fits of multiple sets of data. In summary, the McK–G cooperativity model more uniquely resolves parameters estimated from kinetic and titration data than the Hill model, predicts a sigmoidal dependence of key parameters with calcium concentration, and is simpler and more suitable for practical use.

Item Type: Article
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences
Depositing User: Sue Davies
Date Deposited: 27 Mar 2012 13:36
Last Modified: 20 May 2014 15:40
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