Separation of sialyl-oligosaccharides by high-performance liquid chromatography. Application to analysis of carbohydrate units of acidic oligosaccharides obtained by hydrazinolysis of hen ovomucoid

Sialyl- oligossacharides derived from hen ovomucoid by hydrazinolysis have been separated by liquid chromatography on quaternary amine bonded silica and alkylamine modified silicas . By using a mobile phase consisting of a mixture of acetonitrile and potassium dihydrogen phosphate with 0.01% of 1,4- diaminobutane , effective resolution of high-molecular-weight monosialylated oligossacharides was achieved in less than 2 h.

Monoclonal antibodies as probes of the distribution of ZP-2, the major sulfated glycoprotein of the murine zona pellucida

Three sulfated glycoproteins (ZP-1, ZP-2, and ZP-3) make up the zona pellucida, an extracellular glycocalyx that surrounds mouse oocytes. We have produced five monoclonal antibodies specific to the zona. All five immunoprecipitated ZP-2, and in addition, two of the antibodies immunoprecipitated ZP-3. This suggests the presence of either a common antigenic site or one made up in part by each of the two glycoproteins. The monoclonal antibodies bound to approximately 1.3 X 10(8) binding sites per ovulated mouse egg which represents 2% of the total number of ZP-2 molecules present in the zona. ZP-2 appeared to be present throughout the zona and indirect immunofluorescence revealed a fibrous pattern with no evidence of localization. Furthermore, this pattern of distribution, which was identical for all five monoclones, remained constant after fertilization at the two-cell embryo stage. Laser photobleaching demonstrated that ZP-2 is stably integrated in the extracellular matrix of the zona pellucida. No mouse tissue other than the ovary contained ZP-2 and ZP-2 is antigenically distinct from other previously described extracellular matrix proteins.

Immunological comparison of antibodies to porcine zonae pellucidae in rats and rabbits

Rats and rabbits immunized with porcine zonae pellucidae (ZP) develop antibodies to specific ZP proteins. The proteins recognized by rabbit and rat antibodies were identified using immunoblot procedures. For these studies, proteins were separated by high-resolution, two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Proteins were transferred electrophoretically to nitrocellulose paper and antibody binding determined using 125I-labeled Staphylococcus aureus protein A (Staph A). The three major porcine ZP glycoprotein families were recognized by antibodies in the sera of both rabbits and rats. These antibodies were further characterized using Staph A binding and enzyme-linked (ELISA) immunoassays. Rabbits immunized with porcine ZP developed antibodies which recognized the porcine ZP as well as rat ZP antigens. Rats immunized with porcine ZP produced antibodies which recognized porcine ZP antigens but did not react with rat ZP antigens. While antibodies to porcine ZP, detected by Staph A binding and ELISA assays, correlated with infertility in rabbits [Wood et al. (1981) Biol. Reprod. 25:439], rats having these antibodies could have normal offspring. Continued fertility in rats following immunization with porcine ZP may be due to the failure to induce autoantibodies which recognized self ZP antigenic determinants.

Monoclonal antibodies to rabbit and pig zonae pellucidae distinguish species-specific and shared antigenic determinants

Monoclonal antibodies against rabbit or porcine zonae pellucidae (ZP) demonstrate species-specific and shared antigenic determinants. In addition, these antibodies are used to characterize the biochemical nature of these determinants. All of six monoclonal antibodies developed against porcine ZP react with porcine but not with rabbit ZP. Only one of seven monoclonal antibodies developed against rabbit ZP cross-reacts with porcine ZP. None of these antibodies recognized antigens associated with other tissues tested. High-resolution, two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) followed by immunoblotting was used to demonstrate that the cross-reactive antibody recognizes an antigenic determinant which is associated with the major low molecular weight glycoprotein of both the pig and rabbit ZP. Since this antibody recognizes all charge species of this glycoprotein, it is apparent that the antigenic determinant recognized by this antibody involves protein. Further studies demonstrate that proteolytic digestion of ZP will destroy the antigenic determinant while glycosidic digestion of ZP has no effect on antibody binding. Although polyclonal antibodies to this glycoprotein inhibit sperm from binding to the zona pellucida, this monoclonal antibody does not affect sperm binding. None of the species-specific antibodies recognize ZP glycoproteins following 2D-PAGE. This is a property typical of antibodies directed against conformational antigenic determinants. The presence of common as well as unique zona antigenic determinants could explain why ZP proteins induce heteroantibodies which result in infertility while alloimmunization has no effect on fertility.

Association of sperm receptor activity with a purified pig zona antigen (PPZA)

Three types of data are presented which suggest that sperm receptor activity is associated with a 58,000 Mr acidic glycoprotein (PPZA) isolated from pig zonae: (1) boar sperm fail to bind to pig zonae pretreated with univalent antibody to PPZA; (2) boar sperm pretreated with PPZA are inhibited in binding to intact pig zonae; (3) binding studies utilizing boar sperm and radiolabeled PPZA indicate an inhibition of radiolabeled PPZA binding to sperm by non-labeled PPZA in a dose-related manner. Collectively these data suggest that, at least in the pig system, the contraceptive action of zona antibodies is accomplished by a specific immunologic reaction between antibody and the zona sperm receptor site rather than to a non-specific blockage of this receptor.

Goose lysozyme structure: an evolutionary link between hen and bacteriophage lysozymes?

During evolution, the amino acid sequence of a protein is much more variable and changes more rapidly than its tertiary structure. Given sufficient time, the amino acid sequences of proteins derived from a common precursor may alter to the point that they are no longer demonstrably homologous. The ability to make meaningful comparisons between such distantly related proteins must therefore come primarily from structural homology, and only secondarily (if at all) from sequence homology. On the other hand, structural homology in the absence of sequence homology might be attributed to convergent rather than divergent evolution. (A common fold might be dictated by functional or folding requirements.) We have previously argued, on the basis of structural and functional similarities, that the lysozymes of hen egg-white and bacteriophage T4 have a common evolutionary precursor, even though their amino acid sequences have no detectable similarity. Here we report the structure of the lysozyme from Embden goose, a representative of a third class of lysozymes that has no sequence homology (or perhaps very weak homology) with either the hen egg-white or the phage enzyme. The structure of goose egg-white lysozyme has striking similarities to the lysozymes from hen egg-white and bacteriophage T4. However, some parts of goose lysozyme resemble hen lysozyme while other parts correspond only to the phage enzyme. The nature of the structural correspondence strongly suggests that all three lysozymes evolved from a common precursor.

Carbohydrate structures of hen ovomucoid. A mass spectrometric analysis

The apparently homogenous N-glycosidically-linked glycans 1, 7, 11 and 14 released by hydrazinolysis from hen ovomucoid were analysed by fast atom bombardment and electron-impact mass spectrometry after reduction and permethylation. The spectra support the primary structures established independently [FEBS Letters (1983) 152, 145-152] using methylation analysis, partial acid hydrolysis and 500 MHz 1H NMR spectroscopy. In addition to the major constituents present in fractions 1, 7, 11 and 14, four minor components not detected by other methods could be characterized with the aid of the mass spectrometry data as: Man2GlcNAcGlcNAc-o1, GlcNAc4Man3GlcNAc-o1, GlcNAc6Man3GlcNAc-o1 and GalGlcNAc6-Man3GlcNAc-o1. Our results show that the physical techniques used provide valuable data on the structure of complex glycans. In addition they can be employed to ascertain the homogeneity of the compounds examined as well as to detect trace amounts of homologs that might not be noticed by other methods.

Formation of covalent hybrids from amino-terminal and carboxy-terminal fragments of two ovomucoid third domains

Turkey ovomucoid third domain and Gambel's quail ovomucoid third domain were converted to their modified forms by specific hydrolysis of the Leu18-Glu19 reactive site peptide bond. The modified inhibitors were reduced, yielding in each case two chains, the NH2-terminal 1-18 and COOH-terminal 19-56, which could be separated by gel exclusion chromatography under reducing conditions. The chains were then converted to mixed disulfides with glutathione. The NH2-terminal peptide of turkey domain was mixed with COOH peptide of Gambel's quail domain and allowed to form interchain disulfide bridges to produce "Turbel" hybrid. The hybrid was obtained in 20% yield and was active as a proteinase inhibitor. This modified hybrid could be purified to virtual homogeneity by ion-exchange chromatography. The reactive site peptide bond was then enzymatically synthesized yielding virgin "Turbel" hybrid. The amino acid sequence of this hybrid was in exact accord with expectations. We have shown further that the reactive site hydrolysis, disulfide reduction, reoxidation, and reactive site bond resynthesis cycle do not affect Kassoc for chymotrypsin. Thus, if the results described here are general, we have a useful method for generating many avian ovomucoid third domain variants.

In vitro biosynthesis of three sulfated glycoproteins of murine zonae pellucidae by oocytes grown in follicle culture

The zona pellucida is an extracellular glycocalyx that surrounds the growing oocyte and mediates specific biological functions essential to early mammalian development. We have isolated by a novel technique intact zonae pellucidae from a murine follicle culture system which mimics in vivo granulosa cell-oocyte interactions. Using radioactive precursors we have demonstrated that all three zona proteins, ZP-1, ZP-2, and ZP-3, are sulfated glycoproteins. Incubation of the follicle culture with tunicamycin (0.5 microgram/ml), an antibiotic that blocks N-glycosylation, inhibits new protein deposition in the zona. Under these same conditions overall protein synthesis is decreased only 30%. Biosynthetic studies indicate that after 6 days in culture the zona proteins are produced at 0.4 pg/oocyte/h, which represents 2-3% of the total oocyte protein synthesis. This synthesis stops at or before ovulation and the extremely long half-life (greater than 100 h) of the zona may be essential to preserve its known biological functions, all of which occur after ovulation.

Structural studies of the sugar chains of hen ovomucoid. Evidence indicating that they are formed mainly by the alternate biosynthetic pathway of asparagine-linked sugar chains

The carbohydrate moieties of hen ovomucoid were released as oligosaccharides by hydrazinolysis. The neutral oligosaccharide fraction which comprised about 85% of the total sugar was fractionated into eight oligosaccharide fractions by Bio-Gel P-4 column chromatography. Occurrence of novel penta-antennary oligosaccharides in the larger three fractions was reported in the preceding paper (Yamashita, K., Kamerling, J.P., and Kobata, A. (1982) J. Biol. Chem. 257, 12809-12814). Structural studies of the remaining smaller oligosaccharides indicated that they all have Man alpha 1 leads to 6(Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc as their common core. The alpha-mannosyl residues occur either free or as one of the following five groups: GlcNAc beta 1 leads to 2Man, GlcNAc beta 1 leads to 4Man, GlcNAc beta 1 leads to 4(GlcNAc beta 1 leads to 2)Man, GlcNAc beta 1 leads to 6(GlcNAc beta 1 leads to 2)Man, and GlcNAc beta 1 leads to 6(GlcNAc beta 1 leads to 4)(GlcNAc beta 1 leads to 2) Man. In most oligosaccharides, a beta-N-acetylglucosamine residue is linked at the C-4 position of the beta-mannosyl residue of the core. The structural characteristic of the sugar chains of hen ovomucoid indicated that they are not formed by the ordinary processing pathway of the asparagine-linked sugar chains.

Heteroimmunization of squirrel monkeys (Saimiri sciureus) with a purified porcine zona antigen (PPZA): immune response and biologic activity of antiserum

The potential for utilization as a contraceptive vaccine of a 60,000 Mr glycoprotein component, purified porcine zona antigen (PPZA), isolated from porcine zonae, was investigated in the squirrel monkey. Immunization resulted in production and maintenance of high antibody titers for at least 1 year. Comparable immune profiles were obtained using either monkey or pig zonae in assay systems, but dose-dependent variations in immune response were not observed. In situ antibody binding to monkey zonae was detected, but significantly fewer ovulated eggs were obtained from immunized monkeys than from controls. Exposure of antibody-pretreated pig, monkey, and human zonae to homologous sperm resulted in total inhibition of sperm attachment for the respective species. Thus, the contraceptive potential of PPZA antibodies in these species is demonstrated.

Primary structure of a novel N-glycosidic carbohydrate unit, derived from hen ovomucoid. A 500-MHz 1H-NMR study

The N-glycosidic carbohydrate chains of hen beta-ovomucoid were released from the protein by hydrazinolysis, and separated by HPLC. Primary structural analysis of 3 major fractions was conducted by applying 500-MHz 1H-NMR spectroscopy in combination with methylation analysis. One of the fractions investigated appeared to consist of an intersected penta-antennary structure extended with one Gal residue. The location of the latter in a certain branch could be established unambiguously by NMR. This structure is a novel member of the family of N-glycosidic carbohydrates of glycoproteins.

Human lactotransferrin: molecular, functional and evolutionary comparisons with human serum transferrin and hen ovotransferrin

In this review article, human lactotransferrin is compared to human serum transferrin and hen ovotransferrin. For the first time the possibility of a 6-fold internal homology of the transferrins is raised: a scheme in which 6 domains are defined is reported; two of them with the highest homology seem to be implicated in the 2 iron binding sites of each transferrin. The location of the disulfide bridges of the 3 transferrins and of their prosthetic sugar groups is discussed: some not yet described half-cystine containing lactotransferrin peptides are indicated.

The carbohydrate units of asialo-ovomucoid: their heterogeneity and enzymic degradation

An ovomucoid variant free from sialic acid has been prepared in a pure state by ion-exchange chromatography on DEAE-cellulose. The purified glycoprotein contained 10-11 residues of mannose, 2-3 residues of galactose, and 21 residues of 2-acetamido-2-deoxyglucose. Glycopeptides have been prepared by exhaustive digestion with Pronase followed by ion-exchange chromatography on Dowex 50 (X2) resin. Three fractions were obtained, all with similar contents of mannose and hexosamine but with various contents of galactose. The sugar-aspartic acid ratios indicated that all of the fractions were heterogeneous, the major fraction having mannose-galactose-hexosamine-aspartic acid ratios of 2.6:0.5:5.8:1.0. Cleavage of asialo-ovomucoid with cyanogen bromide and proteolytic digestion of the isolated fragments gave two heterogeneous glycopeptide fractions of similar composition. Both asialo-ovomucoid and the principal glycopeptide fraction were degraded with beta-D-galactosidase, alpha-D-mannosidase, and beta-N-acetylglucosaminidase singly and in sequence. Removal of much of the carbohydrate from asialo-ovomucoid had no appreciable effect on its anti-tryptic activity. By sequential degradation of the glycopeptide, a pentasaccharide core alpha-D-Man-[alpha-D-Man]-beta-D-Man-beta-D-GlcNAc-beta-D-GlcNAc-Asn was obtained. Other structural features revealed by enzymic degradation are discussed.

Sperm-egg interactions in the mouse: sequence of events and induction of the acrosome reaction by a zona pellucida glycoprotein

In this investigation, the interaction of mouse sperm with unfertilized eggs and embryos, solubilized zonae pellucidae isolated from eggs and embryos, and purified zona pellucida glycoproteins ZP1, 2, and 3 (J. D. Bleil, and P. M. Wassarman, (1980b) Dev. Biol. 76, 185-202) has been examined in vitro by light and electron microscopy. The experiments described were carried out in order to determine the temporal sequence of events during sperm-egg interaction in vitro and to identify the component(s) of zonae pellucidae responsible for inducing mouse sperm to undergo the acrosome reaction. "Pulse-chase" analysis of the sequence of sperm-egg interactions revealed that mouse sperm first "attach" loosely and then "bind" tightly to the unfertilized egg's zona pellucida. Binding of sperm to egg zonae pellucidae is followed by induction of the acrosome reaction. Induction of the acrosome reaction can be mediated by the zona pellucida, since solubilized zonae pellucidae isolated from unfertilized eggs were found to be just as effective as the calcium ionophore A23187 in inducing the reaction in vitro. Furthermore, ZP3 purified from zonae pellucidae isolated from unfertilized eggs, but not from two-cell embryos, was also just as effective as either solubilized zonae pellucidae from eggs or ionophore A23187 in inducing the acrosome reaction. ZP1 and 2 from both eggs and embryos, and ZP3 from embryos, had little effect on the extent of the acrosome reaction as compared to control samples. The results of these and other experiments (J. D. Bleil, and P. M. Wassarman, (1980b) Cell 20, 873-882) strongly suggest that, at least in vitro, mouse sperm recognize and bind to ZP3 of egg zonae pellucidae, and that such binding leads to the induction of the acrosome reaction. Modification of ZP3 following fertilization eliminates sperm binding to zonae pellucidae and, consequently, induction of the acrosome reaction is precluded.

The carbohydrate units of asialo-ovomucoid: structural features

The structural features of a heterogeneous glycopeptide fraction from asialo-ovomucoid have been investigated by methylation analysis of the fraction and of products obtained at each stage of its sequential degradation with exo-glycosidases. All glycopeptides in the fraction had a common core-structure beta-D-GlcpNAc-(1 leads to 4)-[beta-D-GlcpNAc-(1 leads to 2)]-alpha-D-Manp-(1 leads to 3)-[beta-D-GlcpNAc-(1 leads to 4)]-[beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 6)]-beta-D-Manp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 4)-beta-D-GlcpNAc leads to Asn. Heterogeneity in the fraction arose from variation in the amount of terminal galactose attached via a hexosaminyl residue to the alpha-D-Manp-(1 leads to 3) residue, and from limited variation in the number of terminal hexosaminyl groups attached to the alpha-D-Manp-(1 leads to 6) residue. One glycopeptide in the fraction contained the unusual feature of two different, triply-substituted mannosyl residues. Other structural features of the glycopeptide are discussed.

A novel type of carbohydrate structure present in hen ovomucoid

Hen ovomucoid is characterized by a high degree of microheterogeneity of its carbohydrate moieties, as was recently demonstrated by hydrazinolysis in combination with high performance liquid chromatography (Paz Parente, J., Strecker, G., Leroy, Y., Montreuil, J., and Fournet, B. (1982) J. Chromatogr., in press). This approach resulted in 17 oligosaccharide-alditol fractions; the major one could be purified to homogeneity. Primary structural analysis of this fraction was carried out by methylation analysis, partial acid hydrolysis, and 500-MHz 1H NMR spectroscopy. Combination of these techniques enabled the unambiguous determination of a novel type of asparagine-bound carbohydrate chain: (formula, see text).

Structural study of the carbohydrate moiety of hen ovomucoid. Occurrence of a series of pentaantennary complex-type asparagine-linked sugar chains

Hen ovomucoid contains a series of novel pentaantennary complex-type asparagine-linked sugar chains which can be classified into three groups, N-1, N-2, and N-3b, N-3b, the structure of which is found as a common (formula, see text) structure in all pentaantennary sugar chains. N-2 is a mixture of three isomeric monogalactosyl derivatives of N-3b, and N-1 is a mixture of two isomeric digalactosyl derivatives of N-3b. Most of the galactoses are beta-linked at the C-4 position of beta-N-acetylglucosamine residues 2 and 4 in the N-3b structure shown above. Small amounts of the galactoses are also linked at the C-4 position of beta-N-acetylglucosamine residue 3.

Circular single stranded phage M13-DNA as a template for DNA synthesis in protein extracts from Xenopus laevis eggs: evidence for a eukaryotic DNA priming activity

Unfractionated protein extracts from activated Xenopus laevis eggs contain all functions required for the chain elongation reactions in replicative DNA synthesis (A.Richter, B. Otto and R.Knippers, 1981, Nucl.Ac.Res. 9, 3793-3807). In order to further explore the DNA synthesizing capacity of this in vitro system and to obtain information on the DNA priming activity in these extracts single stranded phage M13-DNA was used as template for in vitro DNA synthesis. The main results of this investigation are: (i) single stranded circular template DNA is converted to a double stranded DNA form in an alpha-amanitin-insensitive reaction which is absolutely dependent on ribonucleoside triphosphates; (ii) the in vitro synthesized complementary strands are DNA fragments of 1000-2000 nucleotides lengths; (iii) the DNA primase activity copurifies through several column steps and sucrose gradient centrifugation with a DNA polymerase alpha. These activities may therefore be closely associated in a quarternary enzyme complex.

Electron spin echo studies of the copper complexes of conalbumin

Electron spin echo envelope spectroscopy was used to probe the two metal binding sites of Cu(II)-conalbumin. The echo envelope spectrum of Cu(II)-conalbumin-oxalate, with metal ion at either one or both of the binding sites, contains lines arising from the interaction of the electron spin of Cu(II) with bound imidazole, demonstrating histidine ligation to the metal ion. The 13C superhyperfine interaction of bound [13C]oxalate, obtained from the ratio of the electron spin echo envelopes of Cu(II)-conalbumin-[13C]oxalate to that of Cu(II)-conalbumin-[12C]oxalate, is about twice the free precession frequency and indicates a contact interaction between 13C and Cu(II). This study indicates that oxalate is directly coordinated to the metal ion. Over the pH range 7.0 to 10.0, where Cu(II)-conalbumin binds carbonate as an associated anion, the echo envelope spectrum indicates that at least one imidazole ligand is coordinated to Cu(II). Below pH 6.0 and above pH 11.0, imidazole coordination is not observed.

Protein evaluation of mixed diets in young adults, growing pigs, and growing rats

The protein quality of mixed diets was tested using the nitrogen balance technique with a slope-ratio approach in adults, growing pigs, and rats. For diet A (milk, cereals, potatoes, meat, fish, and vegetables) and diet B (milk, cereals, and potatoes) the slope of the regression line, nitrogen balance = f (nitrogen intake) was calculated and expressed in percentage of the slope obtained for diets containing egg white protein. In man, diet A was significantly better than the egg white protein diet which was similar to diet B. In pigs, diets A and B were significantly better than egg white protein. In rats, egg white protein was significantly better than diets A and B. The results are of interest in relation to the recommendations by FAO/WHO regarding adjustment of protein allowance in relation to dietary protein quality.

Refined crystal structure of the molecular complex of Streptomyces griseus protease B, a serine protease, with the third domain of the ovomucoid inhibitor from turkey

We have determined the crystal structure of the molecular complex between Streptomyces griseus protease B (SGPB), a bacterial serine protease, and the third domain of the ovomucoid inhibitor from turkey. Restrained-parameter least-squares refinement of the structure with the 1.8-A intensity data set has resulted in an R factor of 0.125. The carbonyl carbon atom of the reactive bond between Leu-18 and Glu-19 in the inhibitor lies at a distance of 2.71 A from the O gamma atom of the nucleophilic Ser-195 in SGPB; this distance is 0.5 A shorter than a normal van der Waals contact. Unlike the reactive bond in the pancreatic trypsin inhibitor complexed with bovine trypsin, the Leu--Glu bond of the ovomucoid inhibitor is not distorted from planarity towards a pyramidal configuration.

Properties of conserved amino acid residues in tandem homologous protein domains. Hydrogen-1 nuclear magnetic resonance studies of the histidines of chicken ovomucoid

Peaks corresponding to the C6 protons of the four histidine residues (positions 58, 111, 123, and 182) of chicken ovomucoid have been assigned in 1H NMR spectra (360 or 470 MHz) of the native single-chain protein and of fragments of the protein corresponding to its three homologous structural domains. Comparison of the 1H NMR pH titration behavior of these histidine residues and the deuterium exchange rates of their C6-H positions show the following: (1) The chemical shift properties of histidine residues 58, 123, and 182 differ despite the fact that the three residues are located in homologous positions in the three tandem domains. (2) The properties of three of the four histidine residues (58, 111, and 123) do not change appreciably when the domains in which they are located are isolated, indicating that their environments are similar in both the fragment and the native protein. (3) The properties of the fourth histidine (182) differ in the isolated domain and in the native protein. (4) The observed properties of the histidine residues stem primarily from intradomain interactions that remain constant in isolated domains rather than from interactions with neighboring domains; an interdomain interaction is required to explain the behavior of only histidine-182. (5) The chemical shift of histidine-111 is affected by the titration of the side chain of aspartate-98 with pHmid 2.6 in native ovomucoid but not in isolated second domain; the chemical shift of histidine-182 is perturbed by the titration of the carboxyl group of the C-terminal cysteine-186 with pHmid 2.4 in native ovomucoid and pHmid 2.6 in isolated third domain.

Lipid environments in the yolk lipoprotein system. A spin-labeling study of the lipovitellin/phosvitin complex from Xenopus laevis

Lipid/protein and lipid/lipid interactions in the yolk lipoprotein complex from Xenopus laevis were examined by introducing a series of lipid spin-labels into the complex and observing the electron spin resonance spectra as a function of the position of the label along the lipid chains, temperature, pH, and charge on the lipid polar head group. Analyses of the spectra show that, in addition to the expected component arising from lipid associated with protein, a second component with increased segmental flexibility and the greater temperature dependence characteristic of lipid/lipid interactions is observed. These spin-labeling data and supporting compositional data indicate that much of the lipid is organized into a lipid-rich region or pool, consistent with the earlier model derived from electron microscopy and diffraction data and with companion 31P and 2H nuclear magnetic resonance data reported in the preceding paper [Banaszak, L. J., & Seelig, J. (1982) Biochemistry (preceding paper in this issue)]. The bilayer-like component exhibits a greater restriction of motion compared to vesicles of the isolated lipids at the same temperature, as would be expected for a relatively small lipid pool. Phospholipids exchange between the two motionally distinguishable environments. The equilibrium binding undergoes a shift between these two environments as a function both of pH and of the charge on the phospholipid polar head group. This shift in average binding affinity is opposite in direction to that reported for membrane proteins and implicates negatively charged groups on the protein that repel negatively charged phospholipids. This effect is greatly reduced by alkaline phosphatase treatment, suggesting that some of the lipid binding sites are in close proximity to phosphorylated residues on the protein.

Lipid domains in the crystalline lipovitellin/phosvitin complex: a phosphorus-31 and deuterium nuclear magnetic resonance study

The crystalline lipovitellin/phosvitin complex has a molecular weight of 456 000 and contains nearly 100 molecules of bound phospholipid. Earlier work using electron microscopy and three-dimensional image reconstruction methods established the symmetrical dimeric nature of this lipoprotein, but the organization of the lipid was unknown. Under conditions where the lipoprotein is in solution, the high-resolution 31P nuclear magnetic resonance (NMR) spectra contain two well-resolved peaks which can be assigned to phosphoserine moieties in both lipovitellin and phosvitin and to the phospholipid microdomains. The spin-lattice relaxation times, T1, for the phosphoserines and the phospholipid head groups are distinctly different, with the serine phosphates having faster reorientation rates. 31P NMR spectra of crystalline lipoprotein contain a broad symmetric component with a chemical shielding anisotropy of about -50 ppm. By obtaining 31P MNR spectra from several modified forms of the lipoprotein as well as from the extracted lipids, it is shown that the chemical shielding anisotropy is characteristic of phospholipid in a bilayer arrangement. As a further check on 31P NMR results, samples of the lipovitellin/phosvitin complex containing deuterium-labeled 1,2-dielaidoyl-sn-glycero-3-phosphocholine were studied by 2H NMR methods. The resulting spectrum has characteristics similar to those obtained from model lipid systems in a lamellar state. The results of the 31P and 2H NMR experiments correlate with the low-resolution model of the crystalline lipovitellin complex obtained by diffraction studies. It is proposed that each subunit of lipovitellin contains a microdomain of phospholipid in a bilayer-like arrangement.

Protein requirements of young Chinese male adults on ordinary Chinese mixed diet and egg diet at ordinary levels of energy intake

With a total of 28 normal, healthy male adults, N balance studies with both Chinese mixed diet and egg diet were conducted at four protein levels with the former (0.45, 0.55, 0.65 and 0.75 g . kg-1 . day-1) and at three protein levels with the latter (0.35, 0.45 and 0.55 g . kg-1 . day-1) at ordinary levels of energy intake. By regression analysis, the mean maintenance N requirement (PRm) of the mixed Chinese diet calculated was 127.0 mg . kg-1 . day-1 (0.79 g protein . kg-1 . day-1). Estimate a allowance for individual variation to cover the 97.5% population (PR0.975) was 188.1 mg . kg-1 . day-1 (1.18 g protein . kg-1 . day-1). As for the egg diet series, PRm and PR0.975 were 98.2 mg N . kg-1 . day-1 (0.61 g protein . kg-1 . day-1) and 141.6 mg N . kg-1 . day-1 (0.89 g protein . kg-1 . day-1), respectively. Net protein utilization (NPU) of egg diet protein was significantly higher than that of the Chinese mixed diet protein (P less than 0.01), with mean values of 56 versus 43. True digestibility of the mixed diet and egg diet proteins was 96.5 and 98%, respectively. The efficiency of utilization of the Chinese mixed diet protein was 73-77% of the egg protein, based on relative N requirements.

Disulfide bonds in egg-white riboflavin-binding protein. Chemical reduction studies

All eight disulfide bonds in the apo-form of egg white riboflavin-binding protein were easily reduced by 2-mercaptoethanol and dithiothreitol. These bonds exhibited nearly the same reactivity, thus they appeared to be exposed in the native structure, or 'superficial'. The cleavage of protein disulfides resulted in a loss of riboflavin-binding capacity. A correlation between these two related processes, analysed by kinetic and statistical methods, suggested a single bond to be essential for binding of riboflavin by the apoprotein. In the riboflavin-apoprotein complex the disulfides were rather poorly reducible but they still constituted a single reactivity class. The essential bond was not protected against modification, suggesting it was located out of the riboflavin-binding site. A postulated subunit structure of riboflavin-binding protein was not confirmed. The cleavage of disulfides caused some aggregation of the protein molecules. Only dimers and high polymers were formed, the former being relatively stable. Hydrophobic forces were probably involved in the formation of dimers.

Receptor-mediated vitellogenin binding to chicken oocytes

The specific binding of vitellogenin to chicken oocyte membranes was characterized. This major hen serum phospholipoglycoprotein and one of its lower-molecular-weight components, phosvitin, bound to oocyte membranes with KD values of approx. 6 x 10-7 M. The optimum pH for binding was 6.0, the same as the pH of yolk contents. Phosvitin and vitellogenin compete with each other for binding; other proteins tested do not compete to the same degree. Phosvitin, which contains 10% phosphate by weight, appears to be the polypeptide recognized by the receptor. RNA failed to compete with either vitellogenin or phosvitin for binding, suggesting that the binding specificity may require more than polymeric phosphate. The binding was tissue-specific in that phosvitin and vitellogenin bound to oocyte surfaces (at both pH 6.0 and 7.5), but not to chicken erythrocytes (at either pH).

A pmr study of the effects of pH and anion and metal ion binding of the histidyl residues of ovotransferrin

High resolution proton magnetic resonance studies of ovotransferrin show clear resolution of four groups of C(2)-H histidyl resonances to low field of the major aromatic envelope. Titrations of the protein in the absence and presence of synergistic anions, oxalic acid, malonic acid, and 2,6-dipicolinic acid, and anions plus metal ions reveal that six histidines are involved in the binding sites. These histidines, three in each binding site, are near to one another. In each binding site one histidine is involved in binding to anions and two are involved in binding to metal ions.

Affinity chromatography of Streptomyces erythreus trypsin-like enzyme on Japanese quail ovomucoid

For simple, rapid purification of Streptomyces erythreus trypsin-like enzyme (TLE), we examined affinity chromatography with quail ovomucoid (QO) as a ligand of an affinity matrix. We prepared two affinity matrices by the cyanogen bromide method and the oxirane coupling method, and compared their binding efficiencies for TLE using frontal affinity chromatography. The affinity matrix in which QO was immobilized by the cyanogen bromide method showed 30% binding efficiency. However, another matrix, in which QO was immobilized by the oxirane coupling method with the lysine residue of the reactive site blocked by citraconylation, showed 92% binding efficiency. The results suggest that some biologically inactive QO was formed during the coupling reaction by the cyanogen bromide method. When we purified TLE from S. erythreus culture broth by affinity chromatography on QO-Sepharose, TLE was purified about 1,100-fold by affinity chromatography, and was further purified by DEAE-Sephadex A-25 column chromatography to homogeneity. The overall yield of TLE activity was higher than 90%. Thus, we were able to greatly improve previous purification procedures.

The secondary structure of ovomucoid and its domains as studied by circular dichroism

The secondary structure of chicken egg white ovomucoid and its domains was studied by means of circular dichroism (CD). The various domains (domain I, domains II . III, domains I . II, and domain III with and without carbohydrate) were prepared from the ovomucoid by cyanogen bromide cleavage and Staphylococcus aureus protease V-8 digestions. The carbohydrate moiety in the ovomucoid was isolated after its extensive pronase and endo-beta-N-acetyl-glucosaminidase H digestions. On the net CD spectra of polypeptide chain in the ovomucoid and domain preparations, which were obtained by subtracting the spectrum of the carbohydrate moiety from their spectra, the fractions of secondary structure were calculated by the method of Chang et al. (Chang, C.T., Wu, C.S.C. and Yang, J.T. (1978) Anal. Biochem. 91, 13-31). The estimated composition of the secondary structure in the ovomucoid was as follows: alpha-helix, 26%; beta-structure, 46%; beta-turn, 10%; and random coil, 18%. The secondary structure compositions estimated for the three domains suggested that domains I and II were homologous to one another but not to domain III in regard to the proportion of secondary structure content.

Optimalization of the protein content of canned baby-foods based on their nutritive value

When planning canned foods the protein value Net Dietary-protein Energy percent = 8% of a 5-month old infant's requirement was considered as constant. The nutritive value required for this purpose was calculated on the basis of amino acid composition, making use of the Morup-Olesen index. Canned foods were made of two protein-containing components, of sunflower-oil and (occasionally) of starch, by computer, keeping the energy value constant, i. e. 1250 kJ, which covers half of the infant's daily requirement. The optimalization based on the protein value is illustrated by the examples of egg-potato, beef-peas and flour-beans pairs, considering the practical requirements as well.

The effect of complex-formation with polyanions on the redox properties of cytochrome c

1. The stable complex formed between mammalian cytochrome c and phosvitin at low ionic strength was studied by partition in an aqueous two-phase system. Oxidized cytochrome c binds to phosvitin with a higher affinity than reduced cytochrome c. The difference was equivalent to a decrease of the redox potential by 22 mV on binding. 2. Complex-formation with phosvitin strongly inhibited the reaction of cytochrome c with reagents that react as negatively charged species, such as ascorbate, dithionite, ferricyanide and tetrachlorobenzoquinol. Reaction with uncharged reagents such as NNN'N'-tetramethylphenylenediamine and the reduced form of the N-methylphenazonium ion (present as the methylsulphate) was little affected by complex-formation, whereas oxidation of the reduced cytochrome by the positively charged tris-(phenanthroline)cobalt(III) ion was greatly stimulated. 3. A similar pattern of inhibition and stimulation of reaction rates was observed when phosvitin was replaced by other macromolecular polyanions such as dextran sulphate and heparin, indicating that the results were a general property of complex-formation with polyanions. A weaker but qualitatively similar effect was observed on addition of inositol hexaphosphate and ATP. 4. It is suggested that the effects of complex-formation with polyanions on the reactivity of cytochrome c with redox reagents are mainly the result of replacing the positive charge on the free cytochrome by a net negative charge. Any steric effects on polyanion binding are small in comparison with such electrostatic effects.

The origin of protein and fatty yolk in Rana pipiens. V. Unusual paracrystalline configurations within the yolk precursor complex

Three unusual highly ordered configuration of yolk protein in yolk precursor bodies are described. These differ from the crystalline structure of the main body of mature yolk platelets. One of these is an aggregation of paired membranes wih a spacing of about 100 A between the members of a pair. The paired membranes of such an aggregation may be straight, parallel, and very close together; they may appear as a tight whorl; or they may display an intermediate random arrangement with varying distances between pairs. Another configuration is a tubule with a diameter of about 450 A, whose wall appears in cross section to consist of particles measuring 50 X 100 A. A third configuration is a crystalline array of rows of angular-shaped particles with a spacing of about 160 A. It is suggested that these may represent intermediates in the transition of vitellogenin to lipovitellin and phosvitin.

Iron binding by phosvitin and its conformational consequences

With a view to the potential biological significance of iron binding by the phosphoprotein phosvitin, the interaction of these two electrostatically complementary constituents of egg yolk particles was studied by ultrafiltration, circular dichroism, and sedimentation. Ferric complexes of phosvitin are strong and stable; ferrous complexes are weak and dissociate readily. When saturated, pairs of the approximately 135 phosphate groups of a phosvitin molecule appear to bind 1 iron atom each. These findings confirm and extend previous reports regarding the ferric complex and characterize the ferrous complex for the first time. The iron binding sites are not equivalent. Contrary to previous speculations, iron binding is not accompanied by a conformational change from an unordered structure to one of the beta-type. Apparently, neutralization of negative charges, while necessary, is not a sufficient condition of this transition. Nevertheless, iron affects phosvitin structure. Above pH 2, where the protein is unordered but adjusts its average conformation to changes in its net charge as the pH of its solution is varied, iron mimics the effect of protons quantitatively. Near pH 2, where the beta-type conformation is readily acquired by the protein in the absence of iron, the consequences of iron binding upon conformation are determined by the manner in which the iron-phosvitin interaction is brought about. Either the extent of the transition to the "normal" beta-structure becomes limited or the nature of the resulting conformation becomes modified. It is noteworthy that ellipticity changes in the presence of iron do not necessarily occur in parallel at about 200 and 215 nm as they do when the transconformation is produced by pH changes alone. The binding of iron appears to be mostly intramolecular. Intermolecular cross-links become dominant only if most binding sites are filled and then only as a secondary event subsequent to binding and the initial conformational adjustment.

Selective protein transport: identity of the solubilized phosvitin receptor from chicken oocytes

By two independent methods, the solubilized receptor for phosvitin (PV) has a subunit MW of 116K. Affinity chromatography, showed that only 2 of the more than 25 proteins present in the total detergent solubilized oocyte membrane extract were retained on a PV-agarose column. These proteins of MW of 116K and 100K could be eluted from PV-agarose with free PV. By gel exclusion chromatography, the receptor-125I-PV complexes elute in the void volume of a Biogel A-1.5 column. When these void fractions were assayed gy SDS-PAGE only a single protein of MW of 116K was observed in addition to 125I-PV.