Linked Life Data

6327179

Source:http://linkedlifedata.com/resource/pubmed/id/6327179

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PredicateObject
rdf:type
lifeskim:mentions
pubmed:dateCreated
1984-7-11
pubmed:abstractText
Our experiments have delineated the flow of information in the cyclic nucleotide cascade of vision of ROS. A single, photoexcited rhodopsin molecule activates several hundred phosphodiesterase molecules in two stages. First, photoexcited rhodopsin (R*) interacts with transducin (T), a peripheral membrane protein consisting of alpha- (39 kD), beta- (36 kD), and gamma- (approximately 10 kD) subunits. R* catalyzes the exchange of GTP for GDP bound to the subunit of transducin. About 500 T alpha- GTPs are produced per photoexcited rhodopsin at low light levels. T alpha-GTP, released from the beta- and gamma-subunits of transducin, then interacts with the phosphodiesterase to relieve the inhibitory constraint imposed by its gamma-subunit. Hydrolysis of GTP bound to T alpha serves to restore the system to the dark state. Transducin is the amplified signal carrier in this light-triggered cascade. The formation of hundreds of T alpha- GTPs is likely to be the first stage of amplification in visual excitation. The photoactivation of the phosphodiesterase in ROS closely resembles the activation of adenylate cyclase in hormone-sensitive cells. Our cholera toxin labeling studies have shown that transducin is akin to the signal-coupling G protein of the adenylate cyclase system. Cholera toxin specifically ADP- ribosylates and inactivates the GTPase activity of T alpha, just as it does with Gs. The action of pertussis toxin on ROS further underscores the homology of the photoreceptor and hormone-responsive systems. It seems likely that transducin, the stimulatory G protein, and the inhibitory G protein are members of the same family of signal-amplifying proteins. The study of the cyclic nucleotide cascade of vision is proving to be rewarding in affording a view of a recurring motif of signal amplification in nature in addition to providing insight into the mechanism of vision.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:issn
0091-7451
pubmed:author
pubmed:issnType
Print
pubmed:volume
48 Pt 2
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
841-52
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
1983
pubmed:articleTitle
Transducin and the cyclic GMP phosphodiesterase: amplifier proteins in vision.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't