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External IDsGeneCards: [1]
RefSeq (mRNA)



RefSeq (protein)



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Retinol-binding protein 3, interstitial (RBP3), also known as IRBP is a protein that in humans is encoded by the RBP3 gene.[1] RBP3 orthologs [2] have been identified in most eutherians except tenrecs and armadillos.


The inter-photoreceptor retinoid-binding protein is a large glycoprotein known to bind retinoids and found primarily in the interphotoreceptor matrix of the retina between the retinal pigment epithelium and the photoreceptor cells. It is thought to transport retinoids between the retinal pigment epithelium and the photoreceptors, a critical role in the visual process.


The human IRBP gene is approximately 9.5 kbp in length and consists of four exons separated by three introns. The introns are 1.6-1.9 kbp long. The gene is transcribed by photoreceptor and retinoblastoma cells into an approximately 4.3-kilobase mRNA that is translated and processed into a glycosylated protein of 135,000 Da.


The amino acid sequence of human IRBP can be divided into four contiguous homology domains with 33-38% identity, suggesting a series of gene duplication events. In the gene, the boundaries of these domains are not defined by exon-intron junctions, as might have been expected. The first three homology domains and part of the fourth are all encoded by the first large exon, which is 3,180 base pairs long. The remainder of the fourth domain is encoded in the last three exons, which are 191, 143, and approximately 740 base pairs long, respectively.[1]


The rbp3 gene is commonly used in animals as a nuclear DNA phylogenetic marker.[2] The exon 1 has first been used in a pioneer study to provide evidence for monophyly of Chiroptera.[3] Then, it has been used to infer the phylogeny of placental mammal orders,[4][5] and of the major clades of Rodentia,[6] Macroscelidea,[7] and Primates.[8] RBP3 is also useful at lower taxonomic levels, e.g., in muroid rodents[9] and Malagasy primates,[10] at the phylogeography level in Geomys and Apodemus rodents,[11][12] and even for carnivora species identification purposes.[13]

Note that the RBP3 intron 1 has also been used to investigate the platyrrhine primates phylogenetics.[14]


  1. 1.0 1.1 "Entrez Gene: RBP3 retinol binding protein 3, interstitial".
  2. 2.0 2.1 "OrthoMaM phylogenetic marker: RBP3 gene, exon 1".
  3. Stanhope MJ, Czelusniak J, Si JS, Nickerson J, Goodman M (Jun 1992). "A molecular perspective on mammalian evolution from the gene encoding interphotoreceptor retinoid binding protein, with convincing evidence for bat monophyly". Molecular Phylogenetics and Evolution. 1 (2): 148–60. doi:10.1016/1055-7903(92)90026-D. PMID 1342928.
  4. Stanhope MJ, Smith MR, Waddell VG, Porter CA, Shivji MS, Goodman M (Aug 1996). "Mammalian evolution and the interphotoreceptor retinoid binding protein (IRBP) gene: convincing evidence for several superordinal clades". Journal of Molecular Evolution. 43 (2): 83–92. doi:10.1007/BF02337352. PMID 8660440.
  5. Madsen O, Scally M, Douady CJ, Kao DJ, DeBry RW, Adkins R, Amrine HM, Stanhope MJ, de Jong WW, Springer MS (Feb 2001). "Parallel adaptive radiations in two major clades of placental mammals". Nature. 409 (6820): 610–4. doi:10.1038/35054544. PMID 11214318.
  6. Huchon D, Madsen O, Sibbald MJ, Ament K, Stanhope MJ, Catzeflis F, de Jong WW, Douzery EJ (Jul 2002). "Rodent phylogeny and a timescale for the evolution of Glires: evidence from an extensive taxon sampling using three nuclear genes". Molecular Biology and Evolution. 19 (7): 1053–65. doi:10.1093/oxfordjournals.molbev.a004164. PMID 12082125.
  7. Douady CJ, Catzeflis F, Raman J, Springer MS, Stanhope MJ (Jul 2003). "The Sahara as a vicariant agent, and the role of Miocene climatic events, in the diversification of the mammalian order Macroscelidea (elephant shrews)". Proceedings of the National Academy of Sciences of the United States of America. 100 (14): 8325–30. doi:10.1073/pnas.0832467100. PMC 166228. PMID 12821774.
  8. Poux C, Douzery EJ (May 2004). "Primate phylogeny, evolutionary rate variations, and divergence times: a contribution from the nuclear gene IRBP". American Journal of Physical Anthropology. 124 (1): 1–16. doi:10.1002/ajpa.10322. PMID 15085543.
  9. Jansa SA, Weksler M (Apr 2004). "Phylogeny of muroid rodents: relationships within and among major lineages as determined by IRBP gene sequences". Molecular Phylogenetics and Evolution. 31 (1): 256–76. doi:10.1016/j.ympev.2003.07.002. PMID 15019624.
  10. Horvath JE, Weisrock DW, Embry SL, Fiorentino I, Balhoff JP, Kappeler P, Wray GA, Willard HF, Yoder AD (Mar 2008). "Development and application of a phylogenomic toolkit: resolving the evolutionary history of Madagascar's lemurs". Genome Research. 18 (3): 489–99. doi:10.1101/gr.7265208. PMC 2259113. PMID 18245770.
  11. Genoways HH, Hamilton MJ, Bell DM, Chambers RR, Bradley RD (2008). "Hybrid zones, genetic isolation, and systematics of pocket gophers (genus Geomys) in Nebraska". J. Mammal. 89: 826–836. doi:10.1644/07-mamm-a-408.1.
  12. Tomozawa M, Suzuki H (Mar 2008). "A trend of central versus peripheral structuring in mitochondrial and nuclear gene sequences of the Japanese wood mouse, Apodemus speciosus". Zoological Science. 25 (3): 273–85. doi:10.2108/zsj.25.273. PMID 18393564.
  13. Oliveira R, Castro D, Godinho R, Luikart G, Alves PC (June 2009). "Species identification using a small nuclear gene: application to sympatric wild carnivores from South-western Europe". Conserv. Genet. 11 (3): 1023–1032. doi:10.1007/s10592-009-9947-4.
  14. Schneider H, Sampaio I, Harada ML, Barroso CM, Schneider MP, Czelusniak J, Goodman M (Jun 1996). "Molecular phylogeny of the New World monkeys (Platyrrhini, primates) based on two unlinked nuclear genes: IRBP intron 1 and epsilon-globin sequences". American Journal of Physical Anthropology. 100 (2): 153–79. doi:10.1002/(SICI)1096-8644(199606)100:2<153::AID-AJPA1>3.0.CO;2-Z. PMID 8771309.

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