Hormone Receptors (G Protein-Coupled Reactions and Receptor Tyrosine Kinase Receptors) Flashcards
The large diverse family of G protein-coupled receptors respond to a variety of extracellular signals and activate _________.
G proteins
How do G proteins function?
They function as on or off switches for intracellular signalling pathways by activating or inactivating ion channels or effector enzymes that generate second messenger molecules.
GPCR signalling pathways regulate a wide range of cellular activities including: ????
- Metabolism
- Cell division
- Gene expression
The structure of G-protien coupled reactions contain how many transmembrane alpha-helical regions?
Seven
In the structure of G-Protien Coupled Receptors where is the N-termimus is found? The C-terminus?
N-terminus: On the OUTSIDE (ectoplasmic face)
C-terminus: On the CYTOSOLIC face
Ligand-binding site located in a groove located in the _______ of the plane of the membrane.
Middle
Ligand interacts non-covalently with specific amino acids in the ______ - facing side of several membrane-spanning alpha-helixes.
Interior
The G alpha and gamma subunits are linked to the membrane by ____________.
Covalently attached lipids.
Ligand binding alters receptor conformation allowing the binding of the alpha G subunit causing the release of bound _______.
GDP
Describe the six steps associated with the mechanism of GPCR signalling.
- Binding of hormone induces a confirmation change in a receptor.
- Activated receptor binds to the G alpha subunit.
- Activated receptor causes a conformational change in the G alpha, triggering dissociation of GDP.
- The binding of GTP to G alpha triggers the dissociation of G alpha both the receptor and from G bela, gamma.
- The hormone dissociates from the receptor, and G alpha binds to the effector, activating it.
- Hydrolysis of GTP to GDP causes the G alpha to dissociate from the effector and reassociate with the G beta, gamma.
GEF is an ________ protein that is a guanine exchange factor.
Activator
GAP is a GTPase _______ protein.
Accelerating
Guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) regulate the activity of small ______________ to control cellular functions.
Guanine nucleotide-binding (G) proteins
In the case of FRET: Fluorescence Resonance Energy Transfer, cAMP acts as a _________, NOT as a secondary messenger.
Hydrophilic homrone.
True or False. In the case of FRET, activation of a G protein occurs within seconds f ligand binding to its cell-surface G protein-coupled receptor.
True.
G proteins as ON-OFF switches for intracellular signalling pathways by activating ion channels or effector enzymes that generate __________.
Secondary messenger molecules.
True or False? RTKs have a different mechanism action as compared to GPCRs.
True.
Name two types of hydrophilic signalling molecules.
Hormones or peptides.
Hydrophilic signalling molecules (hormones/peptides) activate Receptor Tyrosine Kinases (RTKs), which phosphorylate _______ targets and initiate a signal transduction cascade.
Downstream.
In RTKs, the hormone or peptide leads to _______ of two kinase polypeptides.
Dimerization.
What does the dimerization of RTKs lead to?
Cytoplasmic domain autophosphorylation, which recruits proteins that initiate intracellular signalling pathways.
Describe the activation of RTKS in three steps.
- Receptor tyrosine kinases (RTKS) are first found without a bound ligand.
- The ligand binds. This causes dimerization and phosphorylation of activation loop tyrosines.
- Then, phosphorylation of additional tyrosine residues takes place.
FGF is a fibroblast growth factor. Describe what they are involved in and what they stimulate.
They are involved in wound healing and stimulates cell proliferation and cell spreading.
Describe the two main points associated with activation of the EGF receptor by EGF binding.
When the EGF binds, dimerization alters the conformation of intracellular domain leading to kinase activation. Reciprocal phosphorylation of tyrosine residues on the two cytoplasmic domains of the activated receptor occurs.
Activation of dimerized RTKs leads to _________________, which recruits proteins that initiate intracellular signalling pathways
Cytoplasmic domain autophosphorylation.
There are four HER (Human Epidermal Growth Factor Receptors) that mediate signalling by different members of the ___________.
Epidermal growth factor of hormones.
