RRH

{{Short description|Protein-coding gene in the species Homo sapiens}} {{cs1 config|name-list-style=vanc|display-authors=6}} {{Other uses|RRH (disambiguation)}} {{Infobox_gene}} '''Peropsin''', a visual pigment-like receptor, is a protein that in humans is encoded by the ''RRH'' gene.<ref name="Sun1997">{{cite journal | vauthors = Sun H, Gilbert DJ, Copeland NG, Jenkins NA, Nathans J | title = Peropsin, a novel visual pigment-like protein located in the apical microvilli of the retinal pigment epithelium | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 94 | issue = 18 | pages = 9893–9898 | date = September 1997 | pmid = 9275222 | pmc = 23288 | doi = 10.1073/pnas.94.18.9893 | doi-access = free | bibcode = 1997PNAS...94.9893S }}</ref><ref name="entrez">{{cite web | title = Entrez Gene: RRH retinal pigment epithelium-derived rhodopsin homolog| url = https://www.ncbi.nlm.nih.gov/gene?Db=gene&Cmd=ShowDetailView&TermToSearch=10692}}</ref> It belongs like other animal opsins to the G protein-coupled receptors.<ref name="entrez"/> Even so, the first peropsins were already discovered in mice and humans in 1997,<ref name="Sun1997" /> not much is known about them.<ref name=Guehmann2022>{{cite journal | vauthors = Gühmann M, Porter ML, Bok MJ | title = The Gluopsins: Opsins without the Retinal Binding Lysine | journal = Cells | volume = 11 | issue = 15 | page = 2441 | date = August 2022 | pmid = 35954284 | doi = 10.3390/cells11152441 | pmc = 9368030 | doi-access = free }} 50px Material was copied and adapted from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>

== Photochemistry == Like most opsins, peropsins have in its seventh transmembrane domain a lysine corresponding to amino acid position 296 in cattle rhodopsin,<ref name="Sun1997" /><ref name=Guehmann2022 /> which is important for retinal binding and light sensing.<ref>{{cite journal | vauthors = Leung NY, Thakur DP, Gurav AS, Kim SH, Di Pizio A, Niv MY, Montell C | title = Functions of Opsins in Drosophila Taste | journal = Current Biology | volume = 30 | issue = 8 | pages = 1367–1379.e6 | date = April 2020 | pmid = 32243853 | doi = 10.1016/j.cub.2020.01.068 | pmc = 7252503 | bibcode = 2020CBio...30E1367L }}</ref>

In amphioxus, a cephalochordate, a peropsin binds in the dark-state all-trans-retinal instead of 11-cis-retinal,<ref name=Koyanagi2002>{{cite journal | vauthors = Koyanagi M, Terakita A, Kubokawa K, Shichida Y | title = Amphioxus homologs of Go-coupled rhodopsin and peropsin having 11-cis- and all-trans-retinals as their chromophores | journal = FEBS Letters | volume = 531 | issue = 3 | pages = 525–528 | date = November 2002 | pmid = 12435605 | doi = 10.1016/s0014-5793(02)03616-5 | s2cid = 11669142 | doi-access = free }}</ref> as it is in cattle rhodopsin.<ref>{{cite journal | vauthors = Wald G |title=Carotenoids and the Vitamin A Cycle in Vision |journal=Nature |date=July 1934 |volume=134 |issue=3376 |page=65 |doi=10.1038/134065a0|bibcode=1934Natur.134...65W |s2cid=4022911 |doi-access=free }}</ref><ref>{{cite journal | vauthors = Wald G, Brown PK, Hubbard R, Oroshnik W | title = Hindered Cis Isomers of Vitamin A and Retinene: The Structure of the Neo-B Isomer | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 41 | issue = 7 | pages = 438–451 | date = July 1955 | pmid = 16589696 | doi = 10.1073/pnas.41.7.438 | pmc = 528115 | bibcode = 1955PNAS...41..438W | doi-access = free }}</ref><ref>{{cite journal | vauthors = Brown PK, Wald G | title = The neo-b isomer of vitamin A and retinene | journal = The Journal of Biological Chemistry | volume = 222 | issue = 2 | pages = 865–877 | date = October 1956 | doi = 10.1016/S0021-9258(20)89944-X | pmid = 13367054 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Oroshnik W |title = The Synthesis and Configuration of Neo-B Vitamin A and Neoretinine b | journal = Journal of the American Chemical Society | date = June 1956 | volume = 78 | issue = 11 | pages = 2651–2652 | doi = 10.1021/ja01592a095}}</ref><ref>{{cite journal | vauthors = Oroshnik W, Brown PK, Hubbard R, Wald G | title = Hindered Cis Isomers of Vitamin A and Retinene: The Structure of the Neo-B Isomer | journal = Proceedings of the National Academy of Sciences of the United States of America | date = September 1956 | volume = 42 | issue = 9 | pages = 578–580 | doi=10.1073/pnas.42.9.578| pmid = 16589909 | pmc = 534254 | bibcode = 1956PNAS...42..578O | doi-access = free }}</ref> Therefore, peropsins have been suggested to be photoisomerases.<ref name=Koyanagi2002 />

== Tissue localization == In mice, a peropsin is localized to the apical microvilli of the retinal pigment epithelium (RPE).<ref name="Sun1997" /> There, it regulates storage or the movement of vitamin A from the retina to the RPE.<ref name="Cook2017">{{cite journal | vauthors = Cook JD, Ng SY, Lloyd M, Eddington S, Sun H, Nathans J, Bok D, Radu RA, Travis GH | title = Peropsin modulates transit of vitamin A from retina to retinal pigment epithelium | journal = The Journal of Biological Chemistry | volume = 292 | issue = 52 | pages = 21407–21416 | date = December 2017 | pmid = 29109151 | doi = 10.1074/jbc.M117.812701 | pmc = 5766940 | doi-access = free }}</ref> A peropsin is also expressed in keratinocytes of the human skin. In keratinocyte cell culture, it reacts to UV light if retinal is supplied.<ref>{{cite journal | vauthors = Toh PP, Bigliardi-Qi M, Yap AM, Sriram G, Stelmashenko O, Bigliardi P | title = Expression of peropsin in human skin is related to phototransduction of violet light in keratinocytes | journal = Experimental Dermatology | volume = 25 | issue = 12 | pages = 1002–1005 | date = December 2016 | pmid = 27676658 | doi = 10.1111/exd.13226 | s2cid = 1373924 | doi-access = free }}</ref> In chicken, a peropsin is expressed with an RGR-opsin in the pineal gland and the retina.<ref>{{cite journal | vauthors = Bailey MJ, Cassone VM | title = Opsin photoisomerases in the chick retina and pineal gland: characterization, localization, and circadian regulation | journal = Investigative Ophthalmology & Visual Science | volume = 45 | issue = 3 | pages = 769–775 | date = March 2004 | pmid = 14985289 | doi = 10.1167/iovs.03-1125 }}</ref>

== Gene localization and structure == The human peropsin gene lies on chromosome 4 band 4q25 and has six introns<ref name="entrez"/><ref name=Bellingham2003>{{cite journal | vauthors = Bellingham J, Wells DJ, Foster RG | title = In silico characterisation and chromosomal localisation of human RRH (peropsin)--implications for opsin evolution | journal = BMC Genomics | volume = 4 | issue = 1 | page = 3 | date = January 2003 | pmid = 12542842 | pmc = 149353 | doi = 10.1186/1471-2164-4-3 | doi-access = free }}</ref> like RGR-opsins. However only two of these introns are inserted at the same place, which still indicates that peropsins and RGR-opsins are more closely related to each other than to the ciliary and rhabdomeric opsins.<ref name=Bellingham2003 /> This shared gene structure is also reflected in opsin phylogenies, where peropsins and RGR-opsins are in the same group: The chromopsins.<ref name=Bellingham2003 /><ref name=Guehmann2022 /><ref name="Ramirez2016">{{cite journal | vauthors = Ramirez MD, Pairett AN, Pankey MS, Serb JM, Speiser DI, Swafford AJ, Oakley TH | title = The last common ancestor of most bilaterian animals possessed at least 9 opsins | journal = Genome Biology and Evolution | article-number = evw248 | date = 26 October 2016 | pmid = 27797948 | doi = 10.1093/gbe/evw248 | doi-access = free | pmc = 5521729 }}</ref><ref name="Porter_2011">{{cite journal | vauthors = Porter ML, Blasic JR, Bok MJ, Cameron EG, Pringle T, Cronin TW, Robinson PR | title = Shedding new light on opsin evolution | journal = Proceedings. Biological Sciences | volume = 279 | issue = 1726 | pages = 3–14 | date = January 2012 | pmid = 22012981 | pmc = 3223661 | doi = 10.1098/rspb.2011.1819 }}</ref>

== Phylogeny == The peropsins are restricted to the craniates and the cephalochordates.<ref name=Guehmann2022 /> The craniates are the taxon that contains mammals and with them humans. The peropsins are one of the seven subgroups of the chromopsins. The other groups are the RGR-opsins, the retinochromes, the nemopsins, the astropsins, the varropsins, and the gluopsins.<ref name=Guehmann2022 /> The chromopsins are one of three subgroups of the tetraopsins (also known as RGR/Go or Group 4 opsins). The other groups are the neuropsins and the Go-opsins. The tetraopsins are one of the five major groups of the animal opsins, also known as type 2 opsins). The other groups are the ciliary opsins (c-opsins, cilopsins), the rhabdomeric opsins (r-opsins, rhabopsins), the xenopsins, and the nessopsins. Four of these subclades occur in Bilateria (all but the nessopsins).<ref name=Guehmann2022 /><ref name="Ramirez2016" /> However, the bilaterian clades constitute a paraphyletic taxon without the opsins from the cnidarians.<ref name=Guehmann2022 /><ref name="Ramirez2016" /><ref name="Porter_2011" /><ref name="Liegertová_2015">{{cite journal | vauthors = Liegertová M, Pergner J, Kozmiková I, Fabian P, Pombinho AR, Strnad H, Pačes J, Vlček Č, Bartůněk P, Kozmik Z | title = Cubozoan genome illuminates functional diversification of opsins and photoreceptor evolution | journal = Scientific Reports | volume = 5 | article-number = 11885 | date = July 2015 | pmid = 26154478 | pmc = 5155618 | doi = 10.1038/srep11885 | bibcode = 2015NatSR...511885L }}</ref>

{{gallery |mode=packed |title=The phylogenetic relationship of the peropsins to the other opsins |align=left |height=300 |width=300 |File:Opsin Phylogeny with the main Groups the Tetraopsins Highlighted.svg | Phylogenetic reconstruction of the opsins. The outgroup contains other G protein-coupled receptors. The frame highlights the tetraopsins, which are expanded in the next image. |File:Tetraopsin Phylogeny with the Chromopsins Highlighted.svg |Phylogenetic reconstruction of the tetraopsins. The outgroup contains other G protein-coupled receptors including the other opsins. The frame highlights the chromopsins, which are expanded in the next image. |File:Chromopsin Phylogeny with the Peropsins Highlighted.svg |Phylogenetic reconstruction of the chromopsins. The outgroup contains other G protein-coupled receptors including the other opsins. The frame highlights the peropsins. }}

{{clear}} <!-- The next paragraph should be grouped with the gallery above --> In the phylogeny above, Each clade contains sequences from opsins and other G protein-coupled receptors. The number of sequences and two pie charts are shown next to the clade. The first pie chart shows the percentage of a certain amino acid at the position in the sequences corresponding to position 296 in cattle rhodopsin. The amino acids are color-coded. The colors are red for lysine (K), purple for glutamic acid (E), orange for arginine (R), dark and mid-gray for other amino acids, and light gray for sequences that have no data at that position. The second pie chart gives the taxon composition for each clade, green stands for craniates, dark green for cephalochordates, mid green for echinoderms, brown for nematodes, pale pink for annelids, dark blue for arthropods, light blue for mollusks, and purple for cnidarians. The branches to the clades have pie charts, which give support values for the branches. The values are from right to left SH-aLRT/aBayes/UFBoot. The branches are considered supported when SH-aLRT ≥ 80%, aBayes ≥ 0.95, and UFBoot ≥ 95%. If a support value is above its threshold the pie chart is black otherwise gray.<ref name=Guehmann2022 />

== Clinical significance == Since RGR-opsin may be associated with retinitis pigmentosa,<ref name="Morimura_1999">{{cite journal | vauthors = Morimura H, Saindelle-Ribeaudeau F, Berson EL, Dryja TP | title = Mutations in RGR, encoding a light-sensitive opsin homologue, in patients with retinitis pigmentosa | journal = Nature Genetics | volume = 23 | issue = 4 | pages = 393–394 | date = December 1999 | pmid = 10581022 | doi = 10.1038/70496 | s2cid = 35176366 }}</ref> which is like peropsin also expressed in the retinal pigment epithelium, peropsin was screened for a link with retinitis pigmentosa.<ref name=Ksantini2017>{{cite journal | vauthors = Ksantini M, Sénéchal A, Humbert G, Arnaud B, Hamel CP | title = RRH, encoding the RPE-expressed opsin-like peropsin, is not mutated in retinitis pigmentosa and allied diseases | journal = Ophthalmic Genetics | volume = 28 | issue = 1 | pages = 31–37 | date = March 2007 | pmid = 17454745 | doi = 10.1080/13816810701202052 | s2cid = 225451 | url = https://www.hal.inserm.fr/inserm-00145378/file/Ksantini_et_al._RRH_revised.pdf }}</ref> However, no link could be established.<ref name=Ksantini2017 /><ref>{{cite journal | vauthors = Rivolta C, Berson EL, Dryja TP | title = Mutation screening of the peropsin gene, a retinal pigment epithelium specific rhodopsin homolog, in patients with retinitis pigmentosa and allied diseases | journal = Molecular Vision | volume = 12 | pages = 1511–1515 | date = December 2006 | pmid = 17167409 }}</ref>

== References == {{reflist}}

{{NLM content}} {{Eye proteins}} {{G protein-coupled receptors}}

Category:G protein-coupled receptors