Lecture 10 220 BlkBd

Lecture 10 220 BlkBd - G-protein-linked receptors A) Called...

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Figure 11.7 G-protein-linked receptors A) Called G-protein receptors because they are linked to relay proteins that bind guanosine di- and triphosphate (GDP and GTP) B) When the ligand binds, the G- protein can now bind to the receptor. Its GDP is replaced by GTP. This allows the G-protein move along the membrane to an adjacent enzyme to activate or inhibit it. C) The GTP on the G-protein is then hydrolyzed back to GDP. This deactivates the G-protein and it can now begin a new cycle.
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Figure 11.7 G-protein-linked receptors Where does cAMP fit into this scheme?
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Figure 11.11 G-protein-linked receptors Where does cAMP fit into this scheme?
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CELL COMMUNICATION Extracellular Transduction cascade Response molecules Regulation 1 Regulation 2 Relay protein
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Figure 11.19 A phosphorylation cascade cAMP Regulation 2 Regulation 1
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Figure 11.15 Cytoplasmic response to a signal: the stimulation of glycogen breakdown by epinephrine
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Tyrosine Kinase Receptors These transmembrane receptors are diverse and common. To function they have two components: a) a kinase (which is actually part of the receptor itself) b) a target (or ‘relay’) protein, which is separate from the receptor A functional receptor has two parts, which dimerize when the ligand binds. Dimerization activates the kinase part of receptor. The kinase moves a phosphate group from ATP to a specific amino acid ( tyrosine , serine , or threonine ) located within the cytoplasmic part of the receptor’s polypeptide chain The protein kinase receptor therefore phosphorylates itself ( autophosphorylation ). When phosphorylated in this manner protein kinase receptors then activate relay proteins , again by phosphorylation.
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Figure 11.7 The structure and function of a tyrosine-kinase receptor
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Tyrosine Kinase Receptors The Insulin Receptor The insulin receptor consists of two dimers. Each has an α subunit, which binds the ligand (insulin) outside the cell, and a β subunit, which forms the transmembrane part of the receptor. Two molecules of insulin (one for each α subunit) bind to the receptor. When insulin bind to the
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Lecture 10 220 BlkBd - G-protein-linked receptors A) Called...

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