L10- Cell communication 2 Flashcards
How is signal transduction specific?
Different receptors-ion channel, enzyme coupled receptor, GPCR
Different cell types- neuronal, skin etc.
What MUST signal transduction be?
Transient. Signals can’t last forever
How can transient signal transduction be achieved?
Molecular switches
What do protein kinases act on?
phosphorylate amino acids with the OH groups. Serine, threonine, tyrosine.
If an enzyme works on serine, usually works on threonine too. rarely works on all 3.
What removes phosphates?
Phosphatases
Why does signal amplification happen?
Usually kinases activate other kinases-> cascade
What are the 2 groups of G proteins?
Monomeric- small GTPases eg Ras
Trimeric G proteins
How is the monomeric G protein activated?
The signal comes in, causing the GDP to be replaced by GTP. G protein is now switched on. Signal goes out. GTP hydrolysed to GDP again
What is the structure of the trimeric G protein?
alpha, beta and gamma subunits.
Beta and gamma are attached to the membrane. Alpha is bound to GDP. When activates GTP now attached to alpha and dissociates
What is the common structure for GPCRs?
7 transmembrane domains. Long intracellular loop between 5th and 6th transmembrane domain.
How are GPCRs activated and inactivated?
Activated by ligand binding.
Inactivated by phosphorylation
What do G proteins activate?
Ion channels
Membrane bound enzymes- activates a signalling cascade. As enzymes produce intracellular signalling molecules (2nd messenger)
What is a second messenger?
A rapidly produced diffusable signalling molecule that activates effector proteins
What is one of the most frequent G protein targets?
Adenylate/adenylyl cyclase
What does Adenylate do?
Converts ATP into 2nd messenger cAMP
