Neurobiology April 3

Neurobiology April 3 - Neurobiology April 3, 2008...

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Neurobiology April 3, 2008 Transducin catalyzes reaction of GDP to GTP. The alpha subunit of Transducin bound to GTP activates phosphodiesterase. Phosphodiesterase converts cyclic nucleotides to regular nucleotide. This inhibits. This occurs in rod cells when a photon energizes rhodopsin. In dark cGMP opens cGMP gated channel and allows a calcium and sodium influx, which leads to depolarization. A single photon produces a relatively large electrical event because of amplification. Rhodopsin (photo-activated) gives 500 activated transducins. cGMP gated channel has 4 subunits that come together that form tetramer. Each one has a binding site for cGMP and all subunits must be bound in order for activation and opening. What finally turns off Rhodopsin? When rhodopsin encounters Rhodopsin Kinase, it is phosphorylated and is less likely to react with Transducin. Phosphorylated Rhodopsin can react with arrestin, when arrestin is bound Rhodopsin is no longer active! Calcium is high in the dark and low in the light.
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Neurobiology April 3 - Neurobiology April 3, 2008...

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