Retinol-binding protein , similarity

Papiz, M.Z., et al. The structure of p-lactoglobulin and its similarity to plasma retinol-binding protein. Nature 324 383-385, 1986. 

Lee K.-H., Wells R.G. and Reed R. (1987). Isolation of an olfactory complementary DNA similarity to retinol-binding protein suggests a role in olfaction. Science 253, 1053-1066. 

Godovac-Zimmermann, J., Conti, A., Liberatori, J., and Braunitzer, G. 1985. Homology between the primary structures of beta-lactoglobulins and human retinol-binding protein Evidence for a similar biological function Biol Chem Hoppe Seyler 366(4) 431-434. 

Studies of renal function in stainless steel welders, whose exposure is mainly to chromium(VI) compounds, were negative. Stainless steel welders had significantly increased (p<0.001) levels of urinary chromium, increased clearance of chromium, and increased serum creatinine compared with controls, but no differences were found in the levels of retinol binding protein, p2-microglobulin or other indices of kidney damage (Verschoor et al. 1988). Similar negative results were found in another group of stainless steel welders (Littorin et al. 1984). 

Figure 4.13 Anatomy of selected proteins. (A) The /3 subunit of hemoglobin carrying a heme molecule (B) triose isomerase and (C) /3-lactoglobulin carrying a molecule of vitamin A. Spirals represent helix segments, and the broad arrows are pleated sheet polypeptide segments showing the direction from the N to the C terminus. (A and B reproduced with permission from Richardson JS. The anatomy and taxonomy of protein structure. Adv Prot Chem 34 168-339, 1981. C reproduced with permission from Papiz MZ, Sawyer L, Eliopoulos EE, North ACT, Findlay JBC, Sivaprasadarao R, Jones TA, Newcomer ME, Kraulis PJ. The structure of beta-lactoglobulin and its similarity to plasma retinol-binding protein. Nature 324 383-385, 1986.)...

Alcohol may also act indirectly by causing liver disease, which in turn can affect the capacity of the liver to export vitamin A, thereby enhancing its local toxicity. In alco-hoUcs the carrying capacity of retinol binding protein was increased, even in those with low serum retinol concentrations (97). In such cases, caution in the amount of vitamin A used for therapy is recommended. Similarly, diets that are severely deficient in protein can affect the capacity of the liver to export vitamin A and enhance its hepatotoxicity. 

The overall folding of /3-LG is remarkably similar to that of human plasma retinol-binding protein (Papiz et al., 1986). The core is made up of an eight-stranded antiparallel /3 sheet, which forms a /3 barrel. There is also a short a helix at the C terminus. As described by Monaco et al. (1987), the interior of the /3 barrel is essentially hydrophobic. The conformational difference between the A form and B form of the protein is not significant. The most interesting observation is that the bound retinol molecule interacts with the protein in a way completely different from that of serum retinol-binding protein. The calculated difference map showed that the molecule is not located in the central j3 barrel but binds to the a-heIix//3-barrel interface delimited by about 15 residues. Most of the... 

There are also changes in the binding proteins in plasma as a result of the disease process. Since serum albumin falls in association with any acute iUness, this inevitably leads to a fall in plasma zinc concentration. Similarly a reduction in retinol-binding-protein concentration as part of the APR or protein malnutrition also leads to a fall in serum retinol levels, whatever the amount of retinol stores within the liver. 

The predicted chylomicron retinyl-d4 ester curve is characterized by a sharp peak similar to that of the /3-carotene-dg, again in accord with the expected rapid clearance of chylomicrons foUowing a meal. The predicted plasma retinol-binding protein-retinol-d4 curve shows an initial rise and fall, then a sustained level of retinol-d4 after the /3-carotene-dg dose. This is very similar in shape to that seen when the same subject ingested retinyl-d4 acetate in a previous experiment (Song et oL, 1995). The sustained level of retinol-d4 is a result of the slow release of retinoid into the plasma from... 

To take advantage of the fact that retinol is much more stable when com-plexed with plasma retinol-binding protein, its transport protein, Oliver et al. (43) allowed 200- J,L serum aliquots to dry onto ethanol-washed, dry filter paper. The retinol was redissolved for HPLC analysis by suspending the paper in phosphate buffer, followed by shaking with ethanol, and then extracted with hexane. Shi et al. (44) similarly shipped and stored whole blood or serum samples dried on filter paper, with subsequent analysis by capillary electrophoresis. This procedure allows simple, inexpensive shipment of samples (e.g., population screening surveys) over great distances. 

Papiz M.Z., Sawyer L., Eliopoulos E.E., North A.C.T., Findlay Sivaprasadarao R., Jones T.A., Newcomer M.E., Kraulis P.J. The structure of P-lactoglobulin and its similarity to plasma retinol-binding protein. Nature, 324 383 (1986). 

Protein-Bound Uremic Toxins Among the 20 protein-bound uremic toxins identified in the EUTox review (Vanholder et al., 2003), leptin and retinol binding protein were middle molecules, and 18 others were small solutes (MW < 500 Da). Some of these protein-bound molecules exert a toxic effect at concentrations observed in dialysis patients. For example, the 3-carboxy-4-methyl propylfuranpropionic acid, which is 98% bound to albumin, inhibits erythropoiesis (Niwa et al., 1990). Similarly, P-cresol and indoxyl sulfate, both of which are nearly 100% protein bound, inhibit endothelial... 

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