G protein-coupled receptor kinase 7

Identifiers
Symbol| GRK7
Alt. symbols| GPRK7
NCBI gene| 131890
HGNC| 17031
OMIM| 606987
RefSeq| NM_139209
UniProt| Q8WTQ7
Other data
EC number| 2.7.11.14
Locus| Chr. 3 q24
| Search for

Structures| Swiss-model
Domains| InterPro

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.[1][2][3] This enzyme catalyses the phosphorylation of cone (color) photopsins in retinal cones during high acuity color vision primarily in the fovea.

## More on GRK7

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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).[3] Phosphorylated, light-activated photopsin binds to the cone arrestin protein arrestin-4 to terminate the light-activated signaling cascade.[3] 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.[4][5] 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.[2]

Arrestin-1 bound to rhodopsin in retinal rods prevents rhodopsin activation of the transducin protein to turn off photo-transduction completely.[6] 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

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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. ^ a b 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. ^ a b c 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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