RBP3 regulates atROL taken up by Muller cells

Stable Identifier
Reaction [omitted]
Homo sapiens
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All-trans-retinol (atROL), the product of the reduction of all-trans-retinal (atRAL) released from rod and cone opsins, needs to be regenerated back to the visual chromophore 11-cis-retinal (11cRAL). For the regenerative steps, rods transports atROL back into the retinal pigment epithelium (RPE) while cones utilise Muller cells. Although interphotoreceptor retinoid-binding protein (RBP3, IRBP) (Fong & Bridges 1988, Fong et al. 1990) is not thought to be required to move all-trans-retinol (atROL) from photoreceptor cells to the retinal pigment epithelium (RPE) or Muller cells, it may function to regulate retinoid trafficking and possibly protect retinoids from biochemical damage. RBP3 is secreted by photoreceptor cells into the interphotoreceptor matrix (IPM), where, being a larger protein (135kDa) than the IPM space, becomes trapped (see mini-review Gonzalez-Fernandez & Ghosh 2008). It is through this space that retinoids move between Muller cells and cone photoreceptor outer segments during the cone retinoid cycle.

Literature References
PubMed ID Title Journal Year
3170584 Internal quadruplication in the structure of human interstitial retinol-binding protein deduced from its cloned cDNA

Bridges, CD, Fong, SL

J. Biol. Chem. 1988
2303470 Characterization and comparative structural features of the gene for human interstitial retinol-binding protein

Bridges, CD, Kedzie, KM, Fong, WB, Morris, TA, Fong, SL

J. Biol. Chem. 1990
Catalyst Activity

retinoid binding activity of RBP3 [extracellular region]

Orthologous Events
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