Signalling Transfuction 1 Flashcards
Examples of extracellular signalling molecules
Hormones
Neurotransmitters
Growth factors
For what molecules are receptors intracellular
Steroid
Thyroid hormones
3 superfamilies of cell-surface receptor
G protein-couples (7TM) receptors
Ligand-gated (receptor-operated) ion channels
Receptors with intrinsic enzymatic activity
What follows ligand binding
Activation of receptor
Example of G protein-coupled (7TM) receptors
Muscarinic acetylcholine receptors
Example of ligand-gated ion channels
Nicotine acetylcholine receptors
Example of intrinsic enzymatic activity
Receptor with tyrosine kinases
E.g.) insulin receptor
Difference between agonist and antagonist
Agonist: bind to the receptor and activate it
Antagonist: bind to the receptor, but do NOT activate it
Basic structure of GPCRs
Single polypeptide chain
7-transmembrane spanning regions
Extracellular N-terminal
Intracellular C-terminal
Where are the two regions of GPCRs responsible for ligand binding
Transmembrane
N-terminal region
How do GPCRs reposed to ligands
Conformational change
(Change their 3D shape)
G protein stands for
Guanine nucleotide-binding protein
What are the three subunits of G proteins
Alpha
Beta
Gamma
How do GPCRRs cause a change in cellular activity
GPCR-G protein interaction activates G protein by causing GTP to exchange to GDP on the G protein alpha subunit
Describe the sequence of G-protein signalling
- Agonist-bound receptor binds to G protein
- GDP released from alpha subunit (GDP➡️GTP)
- GTP binds to alpha subunit
- α-βγ complex dissociated into α-GTP and free βγ and each can interact with effector proteins
- GTPase hydrolyses GTP➡️GDP (5secs)
- α-GTP and βγ subunits reform an inactive heterotrimeric complex
