Avian riboflavinuria. 8. The fate of the riboflavin-binding protein-riboflavin complex during incubation of hen's eggs

Egg white proteins

1. Egg white proteins are the principal solutes present in egg white, making up approximately 10% of its weight. 2. They are globular proteins and most have acidic isoelectric points. 3. Many are glycoproteins with carbohydrate contents ranging from 2 to 58%. 4. Of the major egg white proteins, lysozyme is the only one having catalytic activity, but many have specific binding sites, e.g. for vitamins such as biotin, riboflavin and thiamin, or for metal ions such as FeIII. 5. A major group are those showing proteinase inhibitory activity, and they include ovomucoid, ovoinhibitor, cystatin and ovostatin. 6. The synthesis of egg white protein occurs in the oviduct, and is hormonally controlled either by oestrogens or progesterone. 7. Extensive studies have been carried out in the genes coding for egg white proteins.

Pregnancy suppression by active immunization against gestation-specific riboflavin carrier protein

A riboflavin carrier protein isolated from chickens cross-reacts with a gestation-specific rodent carrier for riboflavin. Active immunization of female rats of proved fertility with the purified chicken carrier protein completely yet reversibly suppressed early pregnancy without impairing implantation per se. Concurrently there were no discernible adverse effects on maternal health in terms of weight gain, vitamin status, and fertility.

Distribution and properties of flavokinase in the developing chick embryo

1. Localization of flavokinase was studied in the nonembryonic portions of the chicken egg, in embryos at various stages of development, and in the adult hen. 2. Embryonic biosynthesis of flavin nomonucleotide (FMN) increases with increasing protein synthesis. 3. In the embryo, higher activity of flavokinase was observed in intestine, heart, liver, and yolk sac. 4. Lower activity was observed in allantoic membrane and fluid. 5. No significant activity was measured in yolk. 6. Both specific and total flavokinase activities in organs of the more aerobic and metabolically active adult chicken are considerably greater than those of embryo organs. 7. Flavokinase from embryonic liver was enriched by affinity chromatography by using N-10-flavinyl agarose. 8. The partially purified enzyme has properties generally similar to other animal flavokinases.

Avian riboflavinuria--XI. Immunological quantitation of cross-reacting liver proteins from normal, heterozygous, and mutant hens

A genetic defect, avian riboflavinuria, was discovered in a strain of Single Comb White Leghorn chickens and has been attributed to the absence of functional riboflavin-binding protein (RBP). The ratio of functional RBP in blood, egg yolk, and egg white was 2 (RdRd) : 1 (Rdrd) : 0 (rdrd). The present study on non-riboflavin-binding, cross-reacting proteins (CRPs) from RdRd, Rdrd, and rdrd hens involved partial purification and immunochemical quantitation using antiserum to RBP. Immunoreactivities (microgram/g liver) of CRPs were found to be 2.6 (RdRd) : 1.3 (Rdrd) : 0.02 (rdrd). Reciprocal cross-reactions were observed with rabbit sera directed toward both RdRd CRP and RBP. Reaction of the CRPs with antiglycopeptide serum (specific for beta-linked galactose) showed that they were glycosylated. CRPs from RdRd and Rdrd hens had relative antigenicities similar to that of RBP (Krel approximately or equal to 1), while rdrd CRP had a significantly lower antigenicity (Krel = 0.003). The molecular weights of the CRPs as determined by SDS-polyacrylamide gel electrophoresis were as follows: RdRd = 31,6000, Rdrd = 30,900, and rdrd = 27,500. The molecular weight of egg yolk RBP was 34,7000 by the same method. The conclusion is drawn that the rd gene codes for a nonfunctional mutant protein, possibly an "altered precursor", that is different from RBP.

Isolation and characterization of riboflavin-binding protein from pregnant-rat serum

A high-affinity riboflavin -binding protein was isolated and characterized for the first time from pregnant-rat sera by affinity chromatography on a lumiflavin-agarose column. The purified protein was homogeneous by the criteria of analytical polyacrylamide-gel disc electrophoresis, gel-filtration chromatography on Sephadex G-100 and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. It had a molecular weight of 90000+/-5000 and interacted with [14C]riboflavin with a 1:1 molar ratio with a dissociation constant (Kd) of 0.42 micron.

Calcium-binding proteins in serum of chickens: vitellogenin and albumin

The Ca-binding proteins of hen serum were resolved by gel filtration in 45Ca buffer and were named CaBP(1) and CaBP(2). The major calcium-binding protein, CaBP(1), had a molecular size of 6.0 X 10(5) daltons and appears to be vitellogenin. Deeley et al. (1975) described vitellogenin as the precursor of lipovitellin and phosvitin, the Ca-binding proteins of egg yolk. The present paper demonstrates that "native" vitellogenin is a calcium-binding protein in the serum of laying chickens. The CaBP(2) co-eluted with and was immunologically identical to chicken serum albumin which also bound 45Ca. Data from elution profiles and phosphorus assays indicated that CaBP(1) and CaBP(2) were different from phosvitin and the Ca-binding proteins of the duodenum and uterus.

Calcium-binding proteins in serum: quantitative differences between thick and thin shell lines of chickens

Calcium binding by two proteins, vitellogenin and albumin, was measured in serum of a line of hens producing thick (THK) and a line of hens producing thin shells (THN) as well as a line of commercial hens using gel filtration in 45calcium buffer. Vitellogenin was quantitated in serum of THK and THN using a radial immunodiffusion test. Levels of serum calcium were measured and related to the above mentioned parameters. The binding of vitellogenin was significantly greater in 13 THK than 13 THN (672 vs. 508 cpm/ml X 10(-3), but binding by albumin was not significantly different between the two lines (386 vs. 344 cpm/ml X 10(-3). Binding in 11 commercial hens was similar to that for THN. The THK had significantly greater levels of diffusible, non-diffusible, and total serum calcium than THN. Significant positive correlations between total serum calcium and vitellogenin binding were found in THK (.77) and THN (.81) as well as in the commercial hens (.64). Like vitellogenin binding, levels of vitellogenin were significantly greater in THK than THN (4.0 vs. 1.8 mg/ml). These results suggest that in addition to having more diffusible and non-diffusible serum calcium, THK have more calcium binding and more vitellogenin to perform the binding function than THN.