G-Proteins Flashcards
6 classes of G-proteins
- Rhodopsin like. Most important and the largest.
- Secretin receptor family. Think hormones. Regulated by peptide hormones from the glucagon hormone family.
- Metabotropic glutamate/ pheromone. Neurotransmitter activated hby G protein.
- Fungal mating pheromone
- Cyclic AMP
6 Frizzled/smoothened
7 transmembrane receptors are activated by a wide variety of ligands, including
Light, olfactory stimulants, peptides, hormones, and neurotransmitters.
The human genome encodes ____ 7-TM receptors, of which approximately ___ have an unknown function. They comprise the largest family of receptors in the human genome.
350
150
Which is more common? A disease involving a mutation of the 7TM receptors or disorders which involve antibodies directed at the receptor
Disorders with antibodies targeting the G protein coupled receptor
Typically, disease of the g protein can be caused by
- non functional receptors.
- Consititative activation.
- Changes in ligand binding specificity. Ex: Thyroid stimulating hormone receptor and hyperthyroidism during pregnancy.
- Improper receptor processing of hormones.
- Antibodies directed against receptors. EX; Thyroid stimulation hormone receptor and graves disease.
- Constitutively inactive
Which ligands will diffuse into the cell to bind their nuclear receptor?
Steroids, thyroid, retinoids and 1, 25 dihydroxyvitamin D all diffuse freely into the lipophillic membrane to their nuclear receptor. Typically involved with transcription.
Which ligands will bind to membrane receptors because they are hydrophilic?
Water soluble peptides, catecholamines (Epi and NE), and neurotransmitters.
G-protein coupled receptor
A single polypeptide that is folded into a globular shape and embedded in a cells plasma membrane. Seven segments of this molecule span the entire width of the membrane.
What do G proteins look like that associate with G-protein coupled receptors?
The G protein itself is heterotrimeric, meaning they have 3 different subunits- Alpha, beta, and Gamma.
Alpha and gamma are attached to the plasma membrane by lipid anchors.
G-protein coupled receptors (G proteins plus the 7TM receptor) constistute the largest family in the mammalian genome, accounting for __% of all genes
3-4%
We can study G proteins in ___ for research in breast cancer due to the same G protein expression
Fish
What happens to the GPCR when a ligand binds?
Ligand binding causes GPCRs to undergo a conformational change, which causes the G protein to release GDP in exchange for GTP. This occurs on the alpha subunit and results in its dislocation from beta and gamma.
Which two subunits of the g protein are attached to the membrane by lipid anchors?
Alpha and Gamma
Which subunit of the g protein dissociates from the other two G proteins, after GDP is exchanged for GTP?
Alpha dissociates from beta and gamma.
Light sensitive receptor of rod photoreceptor cells.
Rhodopsin, a well known GPCR.
