Figure 3

A conceptual model of the flow of information within an intracellular signaling network. Biochemical cues initiate a cellular response by interacting with receptors. Cellular receptors modify intermediate signaling proteins via a cascade of activating and deactivating events. Changes in activity of these intermediate signaling proteins ultimately regulate cellular response. In this two level cascade, an activated receptor (R) interacts with signaling protein 1 (S1) to form a multi-protein complex (RS1). The activity of signaling protein 2 is determined by the balance between activation and deactivation rates. The activation and deactivation rates are related to the abundance of the RS1 and deactivating protein (D), respectively. Cellular response is proportional to the activity of signaling protein 2.