Retinolbinding protein

Adler, AJ and Edwards, RB, 2000. Human interphotoreceptor matrix contains serum albumin and retinolbinding protein. Exp Eye Res 70, 227-234. 

Sundaram, M., Sivaprasadarao, A., DeSousa, M.M. and Findlay, J.B.C. (1998) The transfer of retinol from serum retinol-binding protein to cellular retinolbinding protein is mediated by a membrane receptor. Journal of Biological Chemistry 273, 3336—3342. 

Prealbumin (trans- thyretin) 2-3 Binds triiodothyronine and to a lesser extent thyroxine carrier for retinolbinding protein Kidney dysfunction Cirrhosis, hepatitis, stress, inflammation, surgery, hyperthyroidism, cystic fibrosis, kidney dysfunction, zinc deficiency... 

Retinol is secreted by liver in association with plasma retinolbinding proteins. 

Binds triiodothyronine and to a lesser extent thyroxine carrier for retinolbinding protein... 

Chen, C.-C., and Heller, J. (1977). Uptake of retinol and retinoic acid from serum retinolbinding protein by retinal pigment epithelial cells. /. Biol. Chem. 252, 5216-5221. 

Pontuch P> Toserova E, Vozar J, Bulas J, Kratochvilova H. Twenty-four hour ambulatory blood pressure, daytime and nighttime urinary albumin and retinolbinding protein excretion in type I diabetic patients. 

Cell surfaces of body tissues appear to contain receptors for the retinol-binding protein. Many cells also contain cytoplasmic retinolbinding proteins " as well as proteins that bind retinoic acid. 5 These proteins are members of the large superfamily of hydro-phobic transporter molecules described in Box 21-A. This includes the milk protein P-lactoglobulin, which also forms a complex with retinol. ... 

Transthyretin Binds thyroxine (T4) also forms a complex with retinolbinding protein... 

Wang. T. T., Lewis, K. C, and Phang, J. M. (1993). Production of human plasma retinolbinding protein in Escherichia coli. Gene 133,291-294. 

Immunosuppression Binds lipophilic molecules (it is similar to retinolbinding protein and at-acid glycoprotein)... 

Yoon, J. W., Choi, S. H. et al. 2010. Combined impact of adiponectin and retinolbinding protein 4 on metabolic syndrome in elderly people The Korean longitudinal study on health and aging. Obesity 18 826-832. 

Manolescu, D. C., Sima, A., and Bhat, P. V. 2010. All-frans retinoic acid lowers serum retinolbinding protein 4 concentrations and increases insulin sensitivity in diabetic mice. J Nutr 140 311-316. 

Quadro, L., Blaner, W. 8., Hamberger, L. et al. 2002. Muscle expression of human retinolbinding protein (RBP). 8uppression of the visual defect of RBP knockout mice. J Biol Chem 277 30191-30197. 

After uptake of the chylomicron retinyl esters, hydrolysis and reesterification occur in the liver. The resulting retinyl esters (predominantly retinyl palmitate) are stored in the liver and can be mobilized as needed in a highly regulated process. Vitamin A mobilization from hepatic retinyl ester stores takes place as the free alcohol retinol bound to a specific plasma transport protein retinolbinding protein (RBP). 

Retinol is nearly always present in the food in the form of esters which are hydrolysed in the lumen of the intestine. The retinol released is quite readily absorbed into the mucosal cells where it is re-esterified, chiefly with palmitic acid. The retinyl esters are then transported via the lymphatic system into the portal circulation from which they are removed and stored in the liver. Release of the vitamin from the liver depends on the production by the liver of a special retinolbinding protein (RBP). Production of the retinol-binding protein may be disturbed in diseases of the liver or kidneys or in protein/energy malnutrition. In such circumstances retinol cannot be mobilized from the stores and a secondary deficiency may result. Thus it can be seen that the level of retinol in the general circulation is normally highly regulated and is more or less independent of the body s reserves. 

Vitamin A is transported from the gut to the liver in chylomicrons, and from the Hver to the tissues bound to a specific retinal-binding protein or pre-albumin. Deficiency of vitamin A is usually associated with poor protein diets. It is not necessarily reversible by administration of vitamin A alone since the synthesis of retinolbinding protein is affected by the deficiency and therefore so is vitamin A absorption. Deficiency may cause night blindness, xerophthalmia and keratomalacia. Vitamin A toxicity is unUkely with a normal diet but can cause dermatitis, hair loss, and hepatic dysfunction. In pregnancy it can cause teratogenicity if taken in... 

Figure 6.16 Barrel-like conformation adopted by retinolbinding protein p-sheets in order to shield retinol from a hydrophilic environment.

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