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SI session Nov. 15 Ch. 14 and 15 answers

SI session Nov. 15 Ch. 14 and 15 answers - Kaiser Imam BIOL...

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Kaiser Imam November 15, 2007 BIOL 215 SI Session Chapters 14 and 15 Chapter 14: Signal Transduction 1. Receptor tyrosine kinases (RTKs) consist of __ one __ polypeptide chain(s) with __ one __ transmembrane segment(s) in the shape of a(n) __ α-helix __. 2. The cytosolic side of a receptor tyrosine kinase has two parts: a __ tyrosine kinase __ domain and a __ cytosolic tail __ that contains residues of the amino acid __ tyrosine __. 3. The extracellular side of the RTK has a __ ligand binding site __. 4. The binding of a ligand causes receptor tyrosine kinases to __ aggregate __. In situations in which two proteins do this the process is called __ dimerization __. The process by which the RTKs phosphorylate each other in a process called __ autophosphorylation __. 5. The ligand that binds to the RTK to start off the Ras pathway is __ epidermal growth factor (EGF) __. 6. Ras is a __ small monomeric __ G protein that is involved in regulating the __ growth __ and __ division __ of cells. Like many G proteins, Ras is in its active state when it is bound to __ GTP __ and inactive when bound to __ GDP __. The type of protein that makes the exchange of these molecules possible is called a __ guanine-nucleotide exchange factor __. 7. The guanine-nucleotide exchange factor (GEF) that activates Ras is called __ Sos __. This GEF forms a complex with a protein called __ GRB2 __ in order to bind to a receptor tyrosine kinase. 8. Ras can be deactivated by hydrolyzing the GTP molecule bound to it to GDP. This process is mediated by a __ GTPase activating protein (GAP) __. 9. Before its activation by Sos Ras is anchored to the plasma membrane by a __ covalent __ attachment to a __ lipid __ molecule. 10. What are SH2 domains? Give two examples of proteins with SH2 domains that were mentioned in class. SH2 stands for the Src homology domain 2 because its amino acid sequence resembles that of the Src protein. The SH2 domain is a portion of a protein that recognizes and binds to the phosphorylated tyrosine residues created as a result of the autophosphorylation of receptor tyrosine kinases. Specific examples of proteins with SH2 domains include GRB2 and PLC γ . 1
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11. Describe the function of adaptor proteins and give an example. Adaptor proteins can be considered proteins that link one protein to another. In this example adaptor proteins have an SH2 domain on one end that binds to the receptor tyrosine kinase while the other end binds to another protein to be linked. An example of an adaptor protein is GRB2, which links Sos to the RTK. 12. What is the function of growth factors? Name a specific growth factor and describe its origin. Growth factors are secreted molecules that act at a short range and have specific effects on cells possessing receptors that that can detect them. These compounds are normally involved in the growth and reproduction of cells. An example is platelet-derived growth factor (PDGF), which causes the growth of fibroblasts, or cells that promote the formation of scars, after blood clotting. Many of these growth factors bind to receptor tyrosine kinases and start signal transduction pathways to modify gene expression.
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