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G proteins, also known as guanine nucleotide-binding proteins, are a family of proteins that act as molecular switches inside cells, and are involved in transmitting signals from a variety of stimuli outside a cell to its interior. Their activity is regulated by factors that control their ability to bind to and hydrolyze guanosine triphosphate (GTP) to guanosine diphosphate (GDP). When they are bound to GTP, they are 'on', and, when they are bound to GDP, they are 'off'. G proteins belong to the larger group of enzymes called GTPases.
Glucagon is a peptide hormone, produced by alpha cells of the pancreas. It works to raise the concentration of glucose and fatty acids in the bloodstream, and is considered to be the main catabolic hormone of the body. It is also used as a medication to treat a number of health conditions. Its effect is opposite to that of insulin, which lowers extracellular glucose. It is produced from proglucagon, encoded by the GCG gene.
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In molecular biology, the cyclase-associated protein family (CAP) is a family of highly conserved actin-binding proteins present in a wide range of organisms including yeast, flies, plants, and mammals. CAPs are multifunctional proteins that contain several structural domains. CAP is involved in species-specific signalling pathways. In Drosophila, CAP functions in Hedgehog-mediated eye development and in establishing oocyte polarity. In Dictyostelium discoideum, CAP is involved in microfilament reorganisation near the plasma membrane in a PIP2-regulated manner and is required to perpetuate the cAMP relay signal to organise fruitbody formation. In plants, CAP is involved in plant signalling pathways required for co-ordinated organ expansion. In yeast, CAP is involved in adenylate cyclase activation, as well as in vesicle trafficking and endocytosis. In both yeast and mammals, CAPs appear to be involved in recycling G-actin monomers from ADF/cofilins for subsequent rounds of filament assembly. In mammals, there are two different CAPs that share 64% amino acid identity.
Whi2 or Whiskey 2 is a 55 kDa globular, cytoplasmatic scaffold protein in Saccharomyces cerevisiae, which plays an essential role in stress response pathways, apparently by passing input signals about nutrient availability on to stress responsive elements and autophagy/mitophagy mechanisms. It is encoded by a 1.46 kbp gene located on chromosome 15.
Eva Julia Neer (1937–2000) was an American physician, biochemist, and cell-biology scientist who gained U.S. national research awards for her discoveries on G-protein subunit structure and function. She described the physiological roles of these subunits as an integrated and versatile molecular system of signal transduction for membrane-receptor regulation of cell function. Her research concepts turned her into a world leader in G-protein studies and impinged widely on the general understanding of cell behavior.
References
- ↑ "RAS2/YNL098C Protein Information". Saccharomyces Genome Database . Retrieved 4 January 2012.
- ↑ Bhattacharya, Sharmila; Chen, Li; Broach, James R.; Powers, Scott (1995). "Ras Membrane Targeting is Essential for Glucose Signaling but not for Viability in Yeast". Proceedings of the National Academy of Sciences. 92 (7): 2984–8. Bibcode:1995PNAS...92.2984B. doi:10.1073/pnas.92.7.2984. JSTOR 2367245. PMC 42343 . PMID 7708760.
- ↑ Leadsham, Jane E.; Miller, Katherine; Ayscough, Kathryn R.; Colombo, Sonia; Martegani, Enzo; Sudbery, Pete; Gourlay, Campbell W. (2009). "Whi2 links nutritional sensing to actin-dependent Ras-cAMP-PKA regulation and apoptosis in yeast". Journal of Cell Science. 122 (5): 706–15. doi:10.1242/jcs.042424. PMC 2720921 . PMID 19208759.
- ↑ Dong, Jian; Bai, Xiaojia (2011). "The membrane localization of Ras2 and the association between Cdc25p and Ras2-GTP are regulated by protein kinase A (PKA) in the yeast Saccharomyces cerevisiae". FEBS Letters. 585 (8): 1127–34. doi: 10.1016/j.febslet.2011.03.057 . PMID 21457714. S2CID 27110.
- ↑ Sadeh, Amit; Movshovich, Natalia; Volokh, Misha; Gheber, Larisa; Aharoni, Amir (2011). "Fine-tuning of the Msn2/4-mediated yeast stress responses as revealed by systematic deletion of Msn2/4 partners". Molecular Biology of the Cell. 22 (17): 3127–38. doi:10.1091/mbc.E10-12-1007. PMC 3164460 . PMID 21757539.