CAS BI 107 Chapter Notes - Chapter 7: Integral Membrane Protein, Peptide, Phosphodiesterase
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Examples: insulin-controls glucose uptake and metabolism by the cell, epidermal growth factor (egf, platelet-derived growth factor (pdgf) Egf and pdgf regulate cell growth and division in animals: structure (transmembrane receptors) Example of receptors with integral protein kinase activity: If receptor is bound to extracellular signal, ras stays on and the pathway stays on. If receptor becomes unbound to extracellular signal, ras is turned off and pathway shuts off. There exists altered (mutant) forms of ras that have defective gtpase activity; protein is continually on. G protein-one of a large family of heterotrimeric gtp-binding proteins that are important intermediaries in cell-signaling pathways. These protein kinases are activated by the addition of po4 groups to serine or threonine amino acids. Consists of three polypeptide chains associated with cytoplasmic side of the plasma membrane as a heterotrimer: peripheral proteins, alpha chain contains gtp / gdp binding site. Gdp bound; alpha chain bound to beta and gamma chains; alpha chain inactive.