What Is a G-Protein-Linked Receptor?
Rhodopsin is a member of GPCRs superfamily which is pharmacologically important.
Highlights have included solving the first crystal structures of ligand-activated GPCRs—the human β2 adrenergic receptor (β2AR), the avian β1AR and the human A2A adenosine receptor—as well as the structures of opsin and an active form of rhodopsin. These successes followed decades of effort by many laboratories across the world, and are of great interest from the perspectives of membrane-protein biophysics, cell biology, physiology and drug discovery. GPCRs are the largest family of membrane proteins and mediate most cellular responses to hormones and neurotransmitters, as well as being responsible for vision, olfaction and taste. At the most basic level, all GPCRs are characterized by the presence of seven membrane-spanning α-helical segments separated by alternating intracellular and extracellular loop regions. GPCRs in vertebrates are commonly divided into five families on the basis of their sequence and structural similarity.
For crystallographer’s, membrane proteins have always been a nuisance and GPCR’s were especially defiant. In the 90’s there were a series of breakthroughs which allowed the detailed structural characterization of GPCR. The beta-adrenergic receptor (BAR) was a model organism of the GPCR, which was bounded to adrenaline (Katritch, V., Cherezov, V. & Stevens, 2012). This brought about the “fight-or-flight” response among other things. Robert Lefkowitz, in the 80’s introduced “the modern study of GPCRs by first cloning and sequencing the genes for the BARs.”
There also exist a variety of agents that stimulate GPCR activity. The drugs salmeterol and albuterol, which bind to and activate beta-adrenergic GPCRs, stimulate airway opening in the lungs and thus are used in the treatment of some respiratory conditions, including chronic obstructive pulmonary disease and asthma.
Croeze, W. K., Sheffler, D. J., & Roth, B. L. (2003, December 15). G-protein-coupled receptors at a glance. Retrieved December 1, 2018, from http://jcs.biologists.org/content/116/24/4867
Kristiansen, K. (2004, July). Molecular mechanisms of ligand binding, signaling, and regulation within the superfamily of G-protein-coupled receptors: Molecular modeling and mutagenesis approaches to receptor structure and function. Retrieved December 1, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/15251227
Jogalekar, A. (2012, October 10). G Protein-Coupled Receptors (GPCRs) win 2012 Nobel Prize in Chemistry. Retrieved December 1, 2018, from https://blogs.scientificamerican.com/the-curious-wavefunction/g-protein-coupled-receptors-gpcrs-win-2012-nobel-prize-in-chemistry/
Answers Ltd. (2018, November 22). G Protein Coupled Receptors | Essay. Retrieved December 1, 2018, from https://www.ukessays.com/essays/biology/g-protein-coupled-receptors-biology-essay.php
Katritch, V., Cherezov, V. & Stevens, R. C. Diversity and modularity of G protein-coupled receptor structures. Trends Pharmacol. Sci. 33, 17-27 (2012)