An ultrasensitive biomolecular network for robust feedback control

We describe an ultrasensitive reaction network to achieve closed loop control of biomolecular systems. This network is based on non-cooperative interactions of activator and inhibitor species that regulate the controller output level with a mechanism similar to protein phosphorylation. The controller reactions could potentially be realized using nucleic acids or monomeric proteins. Using numerical analysis we demonstrate that ultrasensitivity of the controller output renders the closed loop system robust to perturbations in the system parameters.