Relationship between biotin-binding proteins from chicken plasma and egg yolk.

The plasma of laying hens contains a specific biotin-binding protein that appears to be identical with an egg-yolk biotin-binding protein. Both proteins are saturated with biotin and require elevated temperatures to effect the exchange of [14C]biotin for the protein-bound vitamin. The heat-exchange curve in each case is the same and differs sharply from that of avidin, the egg-white biotin-binding protein. On Sephadex G-100 gel filtration, plasma and yolk biotin-binding proteins were each eluted slightly ahead of avidin (mol.wt. 68,000), suggesting that they are of similar molecular weight. Plasma and yolk biotin-binding proteins required the same ionic strength to be eluted from a phosphocellulose ion-exchange column. Both the plasma and yolk biotin-binding proteins had a pI of 5; avidin has a pI of 10. Plasma biotin-binding protein cross-reacted with antiserum to yolk biotin-binding protein and showed a precipitin line of identity with purified yolk biotin-binding protein. It is suggested that biotin-binding plays an important role in mediating the transport of the vitamin from the bloodstream to the developing oocyte.     

昆虫卵黄蛋白分子进化的研究进展

卵黄原蛋白（Vg）、卵黄多肽（YP）和小卵黄蛋白（minor YP）是昆虫三类主要的卵黄蛋白,它们之间的同源性一直是研究的重点。本文根据已经解析的Vg,YP和minor YP的氨基酸序列,采用序列比对和系统树分析的方法,并结合国内外对三者同源性研究的基础,对其进化关系进行了分析。结果表明,Vg,YP和minor YP是三类具有不同进化祖先的卵黄蛋白,它们的氨基酸序列相似性较低。Vg在系统进化过程中最为保守,与人类的血清载脂蛋白B(ApoB)具有较高的同源性;YP与脊椎动物的肝脂酶和胰脂酶具有较高的同源性;而minor YP与脊椎动物胃脂肪酶和舌脂肪酶具有较高的同源性。同时,对三者的分子特性做了简单的介绍。     

The chicken egg yolk plasma and granule proteomes

Using 1-D SDS-PAGE, LC-MS/MS, and MS(3), we identified 119 proteins from chicken egg yolk, 86 of which were not identified in yolk previously. Proteins were roughly quantitated by calculating their exponentially modified protein abundance index (emPAI) to classify them as major or minor yolk components, and to estimate their distribution between yolk plasma and yolk granular fraction. The proteins with highest abundance were serum albumin, the vitellogenin cleavage products, apovitellenins, IgY, ovalbumin, and 12 kDa serum protein with cross-reactivity to beta2-microglobulin. In addition yolk contained many other serum and egg white proteins, the proteases nothepsin and thrombin, numerous protease inhibitors, and antioxidative enzymes, such as superoxide dismutase and glutathione peroxidase. Among the moderately abundant proteins were two alpha2-macroglobulin-like proteins different from egg white alpha2-macroglobulin, and the major biotin-binding protein of yolk. An unexpected identification was that of the eggshell matrix protein ovocleidin-116, which was previously thought to be eggshell-specific. The list of chicken egg yolk proteins provided in this report is by far the most comprehensive at present and may serve as a starting point for the characterization of less well-known yolk proteins.     

Effects of egg yolk proteins on the longitudinal bone growth of adolescent male rats

Hen egg is a nutritional store for a new life. We examined the effect of egg yolk proteins on longitudinal bone growth in the rat. Protein fractions from egg yolk were tested. Milk protein, casein, was used as a control. The bone growth rate was significantly increased by yolk water-soluble protein (YSP, 100 mg/kg) administration for 5 d. The bone morphogenetic protein-2 immunostaining of growth plate was also increased. Considering the results, YSP can be used as a growth-promoting factor.     

Thermotropic behavior of liposomes from egg yolk lecithin, hydrogenized egg yolk lecithin and their mixtures

The thermotropic properties of multilamellar liposomes from egg yolk lecithin, hydrogenized egg yolk lecithin and several mixtures of these two lipids were studied with the application of excimer--forming optical probe pyrene and microcalorimetry. It was discovered that when the proportion of the egg yolk lecithin in the lipid mixture was raised the temperature of the main phase transition reduced. For all this, independent of the lipid mixture composition when the temperature was raised, apparently, polarity of pyrene microenvironment in the liposomes bilayers decreased. On the basis of the analysis of solidus and liquidus curves obtained from calorimetric studies of the lipid mixtures and bend points of Arrhenius anamorphose obtained during the pyrene excimer formation measurements some conclusions were made about the role of unmodified and hydrogenized egg yolk lecithin cluster formation in the determination of thermotropic properties of the liposomes from the above two lipids mixtures. High temperature phase transition discovered for the egg yolk lecithin while measuring the pyrene excimer formation is proposed to be closely connected with temperature-dependent changes in the organization of phospholipid heads on the interphase bilayer/H2O solution.     

The role of oligosaccharide in transport of egg yolk riboflavin-binding protein to the egg

The carbohydrate portion of chicken egg yolk riboflavin-binding protein was examined to determine its role in the biological activity of the protein. Yolk RBP was found to contain 5–6 mannose, five galactose, 12 N-acetylglucosamine and four sialic acid residues. Specific modifications of the oligosaccharide moiety were performed which included removal of sialic acid by mild acid hydrolysis, oxidation of galactose oxidase, and removal of N-acetylglucosamine and galactose residues by a mixture of glycosidases from Aspergillus niger. All of the modified proteins retained the ability to bind riboflavin although their capacities were lower than that of native yolk RBP. Circular dichroism of the modified yolk RBP samples showed changes in the near ultraviolet, but molar ellipticities in the far ultraviolet displayed only minor variations indicating no gross structural changes. All samples cross-reacted with RBP-specific antiserum. The plasma half-life of ¹²⁵I-labeled yolk RBP was 62 min. Each of the modified samples was cleared more rapidly from the blood than native yolk RBP. Removal of sialic acid decreased the half-life of yolk RBP by 31%, while the other modifications decreased the half-life by as much as 60%. During a 10-day period following injection of ¹²⁵I-labeled yolk RBP, 5.9% of the labeled protein was recovered from egg yolk. Relative to native yolk RBP, the transport of asialo-yolk RBP was decreased by 82%. The other modifications resulted in even less transport to the egg, the lowest being glycosidase-treated asialo-yolk RBP which was decreased by over 99%. By comparison of samples with similar clearance times, a positive correlation was made between sialic acid and ovarian transport.     

31P-NMR characterization of hen egg yolk and egg white

The avian egg is an isolated system where embryonic development can easily be studied. Furthermore, the system can be subjected to various environmental constraints. Its size is such that it can easily be accommodated in most NMR instruments. This is demonstrated by a recent 31P-NMR surface coil experiment where the increase of embryo size and development could be judged by the levels of ATP and phosphocreatine (Belton, P.S., Gordon, R.E., Jones, J.M. and Shaw, D. (1983) Br. Poult. Sci. 24, 429-433).     

Studies of the egg proteins of tropical lizards: purification and partial characterization of yolk proteins of Anolis pulchellus

An easy biochemical procedure for the isolation of lizard lipoprotein is presented as well as the partial characterization of several egg proteins from tropical lizards. In Anolis pulchellus the egg content which is very yolky is homogeneously distributed throughout the egg with no apparent presence of an egg-white. Nevertheless, after resuspension in 0.02 M glycine (pH 7.2), a yolk pellet and a fraction with soluble proteins were separated by low-speed centrifugation. By chromatography in Sephadex G-100, the major egg yolk protein (S-1) was highly purified. This protein was characterized as a glyco-lipo-phosphoprotein with a mol wt of 110,000-120,000 as shown by SDS PAGE. By DEAE cellulose chromatography two acidic proteins (D-5; D-6) were purified (Mr = 62,000-66,000), which do not seem to be components of the yolk granules. Protein D-5 was shown to be a Fe2+-binding protein. By immunochemistry, the liver was found to be the site of synthesis of S-1 and D-5; both proteins are female specific. It is also demonstrated that S-1 shares several chemical and structural properties with the lipovitellins from other oviparous animals.     

Separation of lipid-free egg yolk proteins by high-pressure liquid chromatography using solvents containing formic acid

A method for obtaining total protein patterns from lipid-containing systems, in particular egg yolk, is described. After dispersion of the yolk in 8 M guanidine hydrochloride solution, lipid is removed by extraction with chloroform-methanol and petrol. The protein solution is applied to a high-pressure liquid chromatograph and eluted with a gradient of formic acid, isopropanol, and acetonitrile. In measurements on a known yolk protein, duck apovitellenin I, the method did not cause irreversible formylation of N-terminal or other residues. The method was used (1) to compare protein patterns of whole yolk from hen and quail eggs; (2) to isolate and partially sequence quail apovitellenin I; and (3) to compare protein patterns of "white yolk" and "yellow yolk."