[7] 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 (RPE) and the photoreceptor cells.

[8][9] The human IRBP gene is approximately 9.5 kbp in length and consists of four exons separated by three introns.

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.

[10] Then, it has been used to infer the phylogeny of placental mammal orders,[11][12] and of the major clades of Rodentia,[13] Macroscelidea,[14] and Primates.