signal transduction results in amplification of a signal, a small change at the top can have a large change at the bottom, for example the body can release a small amount of adrenaline (epinephrine)
it is required for translation of cellular signals into events
trimeric means that they are composed of 3 different subunits (alphabet,gamma,beta).
Identify the role of the phospholipase C/Ca2+/protein kinase C pathway in the cell in context with G-protein signalling
Identify the role of the adenylate cyclase/cAMP/protein kinase A pathway in the cell in context with G-protein signalling
adenylate cyclase is produced when adrenaline is released in the body, this then gives rise to cAMP molecules (many cAMP molecules produced by one adenylyl cyclase’s … increased cAMP activates protein kinase A which is a cAMP-dependant protein kinase, PKA
the protein kinase A (cAMP dependant protein kinase) contains 2 catalytic subunits and 2 regulatory subunits (the regulatory subunits act as pseudo substrates< e.g. inhibitors of the active site on the catalytic subunits)
cAMP causes phosphorylation and the regulatory subunits dissociate thereby activating/leaving the active site of the catalytic subunits thereby leaving them free for binding to occur.
explain the mechanism of action of G-proteins
Binding of the ligand changes the receptors conformation which causes it to bind to the G protein’s alpha subunit, in such a way that GDP is displaced and GTP is bound. this triggers ALPHA G-protein subunit dissociation which creates a dimer instead of a trimeractivates downstream pathways.
Activation is short due to GTP hydrolysing to GDP in seconds leading to the re-association of Ga with Gby (sub alpha with gamma and beta) and inactivation of adenylate cyclase(the effector enzyme)
describe the G protein sub units
Gq stimulates phospholipase C
Gs Stimulates adenylate cyclase inc cAMP