ROBUSTNESS IN SIMPLE BIOCHEMICAL NETWORKS

Cells use complex networks of interacting molecular components to tran sfer and process information, These ''computational devices of living cells''(1) are responsible for many important cellular processes, incl uding cell-cycle regulation and signal transduction. Here we address t he issue of the sensitivity of the networks to variations in their bio chemical parameters, We propose a mechanism for robust adaptation in s imple signal transduction networks. We show that this mechanism applie s in particular to bacterial chemotaxis(2-7). This is demonstrated wit hin a quantitative model which explains, in a unified way, many aspect s of chemotaxis, including proper responses to chemical gradients(8-12 ). The adaptation property(10,13-16) is a consequence of the network's connectivity and does not require the 'fine-tuning' of parameters. We argue that the key properties of biochemical networks should be robus t in order to ensure their proper functioning.