Turning Off Amplified Cell Signals

Cell signaling depends on both signal amplification and signal shutoff. When a ligand binds to a cell-surface receptor, the receptor changes shape inside the cell. That change can activate an enzyme function or let the receptor bind other molecules. In many signal transduction pathways, one ligand can trigger many downstream...

Signal transduction pathways use enzymatic cascades to amplify extracellular signals.  

Cells often use kinase cascades to phosphorylate many downstream targets. Some cell-surface receptors, such as receptor tyrosine kinases, have cytosolic domains with kinase activity.

Other receptors lack intrinsic enzymatic activity, bu...