Which one of the following is not a G-protein coupled receptor?
Transferrin receptor
G-protein Coupled Receptors Explained
G-protein coupled receptors (GPCRs) are a large family of cell surface receptors that play a key role in transmitting signals from outside the cell to inside the cell. They respond to a wide variety of external stimuli, including hormones, neurotransmitters, light, and odor molecules. A defining feature of GPCRs is their interaction with intracellular proteins called G proteins upon activation by a signaling molecule.
Let's look at the options provided and determine which type of receptor each represents:
- Epinephrine receptor: Epinephrine (also known as adrenaline) receptors are a type of adrenergic receptor. Adrenergic receptors are well-established members of the G-protein coupled receptor family. They mediate the physiological responses to epinephrine and norepinephrine.
- Transferrin receptor: The transferrin receptor is a transmembrane protein that is crucial for the uptake of iron into cells. It binds to transferrin, a protein that carries iron in the bloodstream, and the complex is internalized through endocytosis. The transferrin receptor is typically a type of receptor that functions through protein-protein interactions and endocytosis, not directly coupling with G proteins for signal transduction. It belongs to a different class of receptors compared to GPCRs.
- Glucagon receptor: The glucagon receptor is a protein found in the membranes of liver and kidney cells. It binds to the hormone glucagon and activates adenylyl cyclase through a G protein, leading to increased cyclic AMP levels. The glucagon receptor is a classic example of a G-protein coupled receptor.
- Thyroid stimulating hormone receptor: The thyroid stimulating hormone (TSH) receptor is found primarily on the surface of thyroid follicular cells. It binds to TSH, a hormone produced by the pituitary gland. The TSH receptor is also a G-protein coupled receptor, mediating the effects of TSH on thyroid hormone production and growth by activating adenylyl cyclase and phospholipase C pathways through associated G proteins.
Based on the functions and mechanisms of these receptors, the epinephrine receptor, glucagon receptor, and thyroid stimulating hormone receptor are all types of G-protein coupled receptors. The transferrin receptor, however, operates through a different mechanism involving endocytosis for iron uptake and is not classified as a GPCR.
Therefore, the receptor that is not a G-protein coupled receptor among the given options is the Transferrin receptor.
Important Questions from Cell signaling
In the table below Column A lists ligands and Column B lists classes of receptors
Column A Column B A Serotonin i Binding activates a G-protein which activates or inhibits an enzyme that generates a specific second messenger and opens ion channel B Interferons ii Binding causes receptor monomers to dimerize. Dimeric receptor then interacts with and activates one or more cytosolic tyrosine protein kinases C Glycine iii Binding changes the conformation of the receptor so that specific ions flow through it D Insulin iv Binding leads to activation of intrinsic tyrosine kinase activity Which one is the correct match?
Receptor for which one of the following proteins spans the plasma membrane of target cells but DOES NOT contain intrinsic protein kinase activity?
Which one of the following amino acids is characteristic of and is conserved in response regulator of plant two-component systems?
Which one of the following signaling molecules is NOT a protein or a peptide?
Receptor tyrosine kinases (RTKs) form a large and important class of cell surface receptors whose ligands are soluble or membrane bound protein or peptide hormones. Which of the following statement is INCORRECT?
