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G-protein-coupled receptor kinase 7 (EC 2.7.11.14, GRK7, cone opsin kinase, iodopsin kinase) is a serine/threonine-specific protein kinase involved in phototransduction. This enzyme catalyses the phosphorylation of cone (color) photopsins in retinal cones during high acuity color vision primarily in the fovea.

More on GRK7

GRK7 is a member of the family of G protein-coupled receptor kinases, and is officially named G protein-coupled receptor kinase 7. GRK7 is found primarily in mammalian retinal cone cells, where it phosphorylates light-activated photopsins, members of the family of G protein-coupled receptors that recognize light of various wavelengths (red, green, blue). Phosphorylated, light-activated photopsin binds to the cone arrestin protein arrestin-4 to terminate the light-activated signaling cascade. The related GRK1, also known as rhodopsin kinase, serves a similar function in retinal rod cells subserving dim light black-and-white peripheral vision outside the fovea. The post-translational modification of GRK7 by geranylgeranylation and α-carboxyl methylation is important for regulating the ability of the enzyme to recognize color opsins in cone outer segment disk membranes.

Arrestin-1 bound to rhodopsin in retinal rods prevents rhodopsin activation of the transducin protein to turn off photo-transduction completely. While cone visual transduction is much less well characterized, it is expected that arrestin-4 bound to GRK7-phosphorylated color photopsin prevents opsin activation of the transducin protein to turn off photo-transduction completely.

References

1. Weiss ER, Raman D, Shirakawa S, Ducceschi MH, Bertram PT, Wong F, Kraft TW, Osawa S (1998). "The cloning of GRK7, a candidate cone opsin kinase, from cone- and rod-dominant mammalian retinas". Mol Vis. 4: 27. PMID 9852166.
2. ^ Chen CK, Zhang K, Church-Kopish J, Huang W, Zhang H, Chen YJ, Frederick JM, Baehr W (December 2001). "Characterization of human GRK7 as a potential cone opsin kinase". Molecular Vision. 7: 305–13. PMID 11754336.
3. ^ Osawa S, Weiss ER (2012). "A Tale of Two Kinases in Rods and Cones". Retinal Degenerative Diseases. Advances in Experimental Medicine and Biology. Vol. 723. Boston, MA: Springer. pp. 821–827. doi:10.1007/978-1-4614-0631-0_105. ISBN 978-1-4614-0630-3. PMC 3632502. PMID 22183412.
4. Shichi H, Somers RL (October 1978). "Light-dependent phosphorylation of rhodopsin. Purification and properties of rhodopsin kinase". The Journal of Biological Chemistry. 253 (19): 7040–6. doi:10.1016/S0021-9258(17)38026-2. PMID 690139.
5. Lorenz W, Inglese J, Palczewski K, Onorato JJ, Caron MG, Lefkowitz RJ (October 1991). "The receptor kinase family: primary structure of rhodopsin kinase reveals similarities to the beta-adrenergic receptor kinase". Proceedings of the National Academy of Sciences of the United States of America. 88 (19): 8715–9. Bibcode:1991PNAS...88.8715L. doi:10.1073/pnas.88.19.8715. PMC 52580. PMID 1656454.
6. Sakurai K, Chen J, Khani SC, Kefalov VJ (April 2015). "Regulation of mammalian cone phototransduction by recoverin and rhodopsin kinase". The Journal of Biological Chemistry. 290 (14): 9239–50. doi:10.1074/jbc.M115.639591. PMC 4423708. PMID 25673692.

This article incorporates text from the United States National Library of Medicine, which is in the public domain.

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