Macular xanthophyll-binding protein (XBP)

Macular xanthophyll-binding proteins (XBPs) are a specialized group of proteins in the human retina responsible for the selective uptake, transport, and stabilization of the xanthophyll carotenoids lutein, zeaxanthin, and meso-zeaxanthin. The primary members of this group include Steroidogenic Acute Regulatory Domain Protein 3 (StARD3), which serves as the specific lutein-binding protein, and Glutathione S-transferase P1 (GSTP1), which acts as the zeaxanthin-binding protein. These proteins concentrate these pigments in the Henle fiber layer and photoreceptor cells, where they collectively form the macular pigment. This pigment acts as a biological "sunglass" by filtering damaging short-wavelength blue light and providing potent antioxidant defense against photo-oxidative damage to the photoreceptors and retinal pigment epithelium. Deficiencies in these binding proteins or low dietary intake of their ligands are strongly linked to an increased risk of age-related macular degeneration (AMD). Therapeutic interventions focus on the use of xanthophyll supplements, such as those in the AREDS2 formulation, which interact with these proteins to enhance the density of the macular pigment and preserve visual function.

Other names

Retinal xanthophyll-binding proteinCarotenoid-binding proteinLutein-binding proteinZeaxanthin-binding proteinStARD3GSTP1MLN64Metastatic lymph node 64 proteinGlutathione S-transferase P1Human retinal lutein-binding protein

Binding and sequestration of xanthophyll carotenoids to provide photoprotection and antioxidant defense in the retina.