G-protein deactivation is rate-limiting for shut-off of the phototransduction cascade

Mandeep S. Sagoo and Leon Lagnado ()
Additional contact information
Mandeep S. Sagoo: MRC Laboratory of Molecular Biology
Leon Lagnado: MRC Laboratory of Molecular Biology

Nature, 1997, vol. 389, issue 6649, 392-395

Abstract: Abstract Photoreceptors detect light through a seven-helix receptor (rhodopsin) and heterotrimeric G protein (transducin) coupled to a cyclic GMP phosphodiesterase1,2. Similar pathways are used to amplify responses to hormones, taste and smell3,4,5. The amplification of phototransduction is reduced by a fall in cytoplasmic Ca2+ (refs 6, 7, 8, 9, 10), but it is not known how the deactivation of rhodopsin and transducin influence this response and hence the extent and duration of phosphodiesterase activity11,12,13,14. Here we investigate this by recording the electrical response to flashes of light in truncated rod photoreceptors10. By removing ATP to block the deactivation of rhodopsin by phosphorylation15, we show that this reaction limits the amplitude of the response and begins within 3.2 s of a flash in a solution containing 1 μM Ca2+, falling to 0.9 s in a zero-Ca2+ solution. In contrast, the activation and amplitude of the response were unaffected when transducin deactivation by GTP hydrolysis was blocked by replacing GTP with its non-hydrolysable analogue GTP-γS11, demonstrating that there is little GTP hydrolysis occurring over the period in which photoexcited rhodopsin is quenched. The rapid deactivation of rhodopsin is therefore a Ca2+-sensitive step controlling the amplitude of the light response, whereas transducin deactivation is slower and controls recovery.

Date: 1997
References: Add references at CitEc
Citations:

Downloads: (external link)
https://www.nature.com/articles/38750 Abstract (text/html)
Access to the full text of the articles in this series is restricted.

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:nat:nature:v:389:y:1997:i:6649:d:10.1038_38750

Ordering information: This journal article can be ordered from
https://www.nature.com/

DOI: 10.1038/38750

Access Statistics for this article

Nature is currently edited by Magdalena Skipper

More articles in Nature from Nature
Bibliographic data for series maintained by Sonal Shukla () and Springer Nature Abstracting and Indexing ().