BE230_Lecture_18&19

BE230_Lecture_18&19 - Cell Structure & Function...

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Cell Structure & Function BE230 Dr Christine Loscher Lecture 7/8
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G protein linked receptors largest family of cell-surface receptors and are found in all eukaryotes It is remarkable that about half of all known drugs work through G-protein-linked receptors. mediate the responses to an enormous diversity of signal molecules, including hormones, neurotransmitters, and local mediators The signal molecules that activate them are as varied in structure as they are in function: includes proteins and small peptides, as well as derivatives of amino acids and fatty acids. The same ligand can activate many different receptor family members; eg. at least 9 distinct G-protein- linked receptors are activated by adrenaline.
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G protein linked receptors Despite the chemical and functional diversity of the signal molecules that bind to them, all G- protein-linked receptors have a similar structure. They consist of a single polypeptide chain that threads back and forth across the lipid bilayer seven times and are therefore sometimes called serpentine receptors In addition to their characteristic orientation in the plasma membrane, they have the same functional relationship to the G proteins they use to signal the cell interior that an extracellular ligand is present.
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G protein linked receptor
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When extracellular signaling molecules bind to serpentine receptors, the receptors undergo a conformational change that enables them to activate trimeric GTP-binding proteins (G proteins) . These G proteins are attached to the cytoplasmic face of the plasma membrane, where they serve as relay molecules, functionally coupling the receptors to enzymes or ion channels in this membrane. There are various types of G proteins, each specific for a particular set of serpentine receptors and for a particular set of downstream target proteins in the plasma membrane. All have a similar structure and operate in a similar way.
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This note was uploaded on 01/05/2010 for the course FSH BT taught by Professor Ianmarison during the Fall '09 term at Dublin City University.

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BE230_Lecture_18&19 - Cell Structure & Function...

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