Calmodulin: calcium, potassium, and magnesium ion multiple equilibria and kinetics for interconversion, including the effect of repeated stimulation |
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Authors: | A Delville P Laszlo D J Nelson |
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Institution: | Institut de Chimie Organique et de Biochimie, Université de Liège au Sart-Tilman, 4000 Liège, Belgium |
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Abstract: | Using computer simulations, with realistic values for the intrinsic thermodynamic binding constants and kinetic on and off rate constants at the four metal-binding sites, the calmodulin molecule is shown to have been optimally adjusted by evolution for biological function. Despite a very large number of potential molecular states, depending upon occupation by potassium, calcium, or magnesium ions, the system restricts itself to a small number of physiologically-significant equilibrium species. It appears to possess built-in triggers for biological processes, with rapid (approximately 20 ms time-scale), step-function shaped, changes of the populations of the CMKK, CMMK, CKKK, CMMM (and CCKK) states. The time-response of calmodulin to periodic changes in ionic levels (2 and 5 s-1) makes it quite adequate for repeated stimulations. In short, calmodulin appears as a very selective information transmitter at the molecular level. |
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Keywords: | To whom correspondance should be addressed |
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