BE230_Lecture_15&16

BE230_Lecture_15&16 - Cell Structure & Function...

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Cell Structure & Function BE230 Dr Christine Loscher Lecture 4/5 Receptors & signal relay
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Three Largest Classes of Cell-Surface Receptor Proteins Ion-Channel-linked, G-Protein-linked, and Enzyme-linked Receptors three classes - defined by the transduction mechanism they use. Cell-surface receptor proteins act as signal transducers. They convert an extracellular ligand- binding event into intracellular signals that alter the behaviour of the target cell (response)
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Ion-channel-linked receptors ( transmitter-gated ion channels or ionotropic receptors) involved in rapid synaptic signaling between electrically excitable cells mediated by a small number of neurotransmitters that transiently open/close an ion channel formed by the protein to which they bind briefly changing the ion permeability of the plasma membrane and thereby the excitability of the postsynaptic cell.
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G-protein-linked receptors act indirectly to regulate the activity of a separate plasma- membrane-bound target protein - can be either an enzyme or an ion channel. The interaction between receptor and target protein is mediated by a third protein - trimeric GTP-binding protein (G protein) activation of target protein can change the conc of one or more intracellular mediators (if the target protein is an enzyme) or can change the ion permeability of the plasma membrane (if the target protein is an ion channel). The intracellular mediators affected act in turn to alter the behaviour of yet other signaling proteins in the cell
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Enzyme-linked receptors when activated, either function directly as enzymes or are directly associated with enzymes that they activate They are formed by single-pass transmembrane proteins that have their ligand-binding site outside the cell and their catalytic or enzyme-binding site inside. The great majority are/associated with protein kinases - ligand binding to them causes the phosphorylation of specific sets of proteins in the target cell.
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Most Activated Cell-Surface Receptors Relay Signals Via Small Molecules and a
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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_15&16 - Cell Structure & Function...

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