Phosphorylation Rheostat

Science  01 Jul 2005:
Vol. 309, Issue 5731, pp. 15j
DOI: 10.1126/science.309.5731.15j

The modulation of the activity of proteins by phosphorylation has often been described as a binary switch, but Pufall et al. (p. 142) show that finer rheostat-like control can also be achieved. The transcription factor Ets-1 exhibits a graded DNA binding affinity that depends on the number of sites that are phosphorylated. Ets-1 exists in conformational equilibrium between a dynamic conformation that binds DNA and a well-folded inhibited state. Increasing phosphorylation progressively shifts the equilibrium toward the inhibited state and thus fine-tunes the level of activity. The phosphorylated region, which serves as the allosteric effector, is predominantly unstructured and flexible, and probably acts through transient interactions.

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