TABLE 1.
Macrodescription of signaling modules
| Estimation of microstates in terms of macrostates
|
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|---|---|---|---|---|
| System properties | Definition of macrostates | Is macrostate description exact? | During the time- evolution of the system | At the steady-states |
| A scaffold with kinetically independent docking sites. No controlling hierarchy, no allosteric interactions or interactions through bound partners. | A macrostate is the sum of all microstates having a particular state of a docking site. | Yes. | Exact. | Exact. |
| A scaffold-receptor module. Docking sites on the scaffold do not interact allosterically or through bound partners. The state of a controlling site (h) on the scaffold influences the chemical transformations of docking sites. | A macrostate is the sum of all microstates having a particular state of a docking site and a certain state h. | Yes. | Approximate. The accuracy of the approximation is higher if the changes in h-states occur much faster than the transformations of docking sites. | Approximate. The accuracy of the approximation is higher if the changes in h-states occur much faster or much slower than the transformations of docking sites. |
| A receptor acting as a scaffold with independent docking sites. Ligand-receptor interactions are independent of the states of receptor docking sites. The state of a controlling site (h) is determined by ligand binding and affects the docking sites. | A macrostate is the sum of all microstates having a particular state of a docking site and a certain state h. | Yes. | Approximate. The accuracy of the approximation is higher if the changes in h-states occur much faster than the transformations of docking sites. | Approximate. The accuracy of the approximation is higher if the changes in h-states occur much faster or much slower than the transformations of docking sites. |
| A receptor that acts as a scaffold with independent sites. No controlling hierarchy (no h-sites), but ligand dissociation occurs only if all docking sites on the receptor are unphosphorylated. | A macrostate is the sum of all microstates of the receptor with bound ligand and a particular state of a docking site. | No. Only an approximate macro-description. | Approximate, usually with high accuracy. | Exact. |
| Each site influences any other site, either directly or indirectly (via a bound partner). | Macrodescription is not applicable. | |||