User:Dudleydoodog/Transducin
Article Draft[edit]
Although the traditional mechanism involves activation of PDE by GTP-bound Tα, GDP-bound Tα has also been demonstrated to have the ability to activate PDE. Experiments of PDE activation in the dark (without the presence of GTP) show small but reproducible PDE activation.[1] This can be explained by the activation of PDE by free GDP-bound Tα. PDE γ subunit affinity for GDP-bound Tα, however, seems to be about 100-fold smaller than for GTP-bound Tα.[2] The mechanism by which GDP-bound Tα activates PDE remains unknown however, it is speculated to be similar to the activation of PDE by GTP-bound Tα.[1] Tα can accelerate the rate of activation of light-off induced Protein Kinase A due to binding to rhodopsin . [3] As well as, transducin achieves full functional activation upon binding to activated rhodopsin.[4]
There are different isoforms of Tα, seen in rod and cone cells. However, the isoforms exhibit functional interchangeability in the phototransduction cascade and shouldn't solely account for differences in light sensitivity.[5] Although the focus for phototransduction is on Tα, Tβγ is crucial for rhodopsin to bind to transducin.[6][7] The rhodopsin/Tβγ binding domain contains the amino and carboxyl terminal of the Tα. The amino terminal is the site of interaction for rhodopsin while the carboxyl terminal is that for Tβγ binding. The amino terminal might be anchored or in close proximity to the carboxyl terminal for activation of the transducin molecule by rhodopsin.[8]
References[edit]
- ^ a b Kutuzov, M.; Pfister, C. (1994). "Activation of the retinal cGMP-specific phosphodiesterase by the GDP-loaded alpha-subunit of transducin". European Journal of Biochemistry. 220 (3): 963–971. doi:10.1111/j.1432-1033.1994.tb18700.x. PMID 8143750.
- ^ Bennett, N.; Clerc, A. (1989). "Activation of cGMP phosphodiesterase in retinal rods: Mechanism of interaction with the GTP-binding protein (transducin)". Biochemistry. 28 (18): 7418–7424. doi:10.1021/bi00444a040. PMID 2554970.
- ^ Sato, Shinya (October 27, 2020). "Rhodopsin-mediated light-off-induced protein kinase A activation in mouse rod photoreceptor cells". Proceedings of the National Academy of Sciences of the United States of America. 117 (43): 1.
- ^ Ernst, Oliver (June 26, 2006). "Monomeric G Protein-Coupled Receptor Rhodopsin in Solution Activates Its G Protein Transducin at the Diffusion Limit". Proceedings of the National Academy of Sciences of the United States of America. 104 (26): 5.
- ^ Deng, Wen-Tao (October 20, 2009). "Functional Interchangeability of Rod and Cone Transducin α-Subunits". Proceedings of the National Academy of Sciences of the United States of America. 106: 2.
- ^ Fung, B. K. (1983). "Characterization of transducin from bovine retinal rod outer segments. I. Separation and reconstitution of the subunits". The Journal of Biological Chemistry. 258 (17): 10495–10502. doi:10.1016/S0021-9258(17)44483-8. PMID 6136509.
- ^ Kisselev, O. G.; Downs, M. A. (2003). "Rhodopsin controls a conformational switch on the transducin gamma subunit". Structure. 11 (4): 367–373. doi:10.1016/s0969-2126(03)00045-5. PMID 12679015.
- ^ Hingorani, V. N.; Ho, Y. K. (1987). "A structural model for the alpha-subunit of transducin. Implications of its role as a molecular switch in the visual signal transduction mechanism". FEBS Letters. 220 (1): 15–22. doi:10.1016/0014-5793(87)80867-0. PMID 3038611. S2CID 33255299.