- After the ligand binds, the intracellular domain of the receptor protein changes shape, initiating transduction of the signal by converting it into a form that causes cell response
- Main Idea: molecules interact with each other to relay/amplify signal
SECOND MESSENGERS
- Small, non-protein molecules that spread through cell via diffusion and relay/amplify the intracellular signal
2nd Messenger: Cyclic AMP (cAMP)
- Created using adenylyl cyclase by cutting ATP and two phosphates
- Can activate protein kinase→ Cell response
2nd messenger: Ca+
- Ca+ levels stimulate cellular response
- Cell regulates concentration by actively transporting into ER and mitochondria
Signaling Cascade
- Many signal transduction pathways include protein modification and phosphorylation cascades
- Kinase cascade or phosphorylation cascade: Series of enzymatic reactions where a kinase enzyme phosphorylates molecules which phosphorylates another molecule, etc.
- Benefits: amplify so that small signal made bigger, better regulation/control
- Signaling cascades relay signals from receptors to cell targets → amplify incoming signals → result in appropriate cell response
- Scaffold Proteins: large relay proteins attached to each other which improve efficiency of signaling cascade by holding participating enzymes in close proximity
- Scaffolding also used to keep members of one signaling cascade isolated from members of another cascade
