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At least 19 recordsLinked to original sources
PubMed1996

Co-integration of beta-lactoglobulin/human serum albumin hybrid genes with the entire beta-lactoglobulin gene or the matrix attachment region element: repression of human serum albumin and beta-lactoglobulin expression in the mammary gland and dual regulation of the transgenes.

The effect of co-integration of the entire beta-lactoglobulin (BLG) gene or matrix attachment region (MAR) sequences on the expression of various BLG/ human serum albumin (HSA) gene constructs was tested in transgenic mice. These former sequences were chosen because of their reported ability to insulate transgenes from the neighboring host genomic DNA sequences and/or to provide a more permissive transcriptional environment. When introduced alone, a cDNA-based BLG/HSA construct was expressed in 60% of transgenic strains and HSA was secreted at levels up to 0.3 mg/ml into the milk. Upon co-integration with either the entire BLG gene or MAR element, HSA RNA and protein expression were completely abrogated. While the co-integrated BLG gene suppressed the proportion of expresser strains carrying cDNA as well as genomic BLG/HSA constructs, the MAR element only exerted its negative effect on the cDNA-based BLG/HSA construct. In transgenics expressing both HSA and BLG, the tissue specificity and developmental patterns of BLG expression were altered and resembled the less stringent pattern of the BLG/HSA expression. These results demonstrate that rescue of transgene expression through co-integration with BLG or MAR sequences do not apply universally.

Animals↗
PubMed1985

The amino-acid sequence of beta-lactoglobulin II from horse colostrum (Equus caballus, Perissodactyla): beta-lactoglobulins are retinol-binding proteins.

beta-Lactoglobulin isolated from horse colostrum is heterogeneous and contains two components: beta-lactoglobulin I and beta-lactoglobulin II. These two proteins are monomeric and show differences in their electrophoretic mobilities, chain lengths and primary structures. The complete amino-acid sequence of beta-lactoglobulin II was determined by automated Edman degradation of the intact protein and of the peptides derived from these by digestion with trypsin or chymotrypsin and by chemical cleavage with cyanogen bromide. Unlike other beta-lactoglobulins which contain 162 amino acids, horse beta-lactoglobulin II is unique in that it contains 166 amino acids. The additional four amino acids represent an insertion between positions 116 and 117 of other beta-lactoglobulins so far sequenced, including horse beta-lactoglobulin I. Sequence comparison of beta-lactoglobulins I and II from horse colostrum reveals 48 amino acid substitutions (30%). Such a diversity between members of the beta-lactoglobulin gene family has not been encountered before. Sequence comparison with bovine beta-lactoglobulin A shows 85 amino acid replacements accounting for 53% of the residues. The structural homology with human retinol-binding protein may reveal similar biological functions and clues to the origin of milk proteins.

Amino Acid Sequence↗
PubMedDate not supplied

Isolation of lactoperoxidase, lactoferrin, alpha-lactalbumin, beta-lactoglobulin B and beta-lactoglobulin A from bovine rennet whey using ion exchange chromatography.

A mild and rapid method is described for isolating various milk proteins from bovine rennet whey. beta-Lactoglobulin from bovine rennet whey was easily adsorbed on and desorbed from a weak anion exchanger, diethylaminoethyl-Toyopearl. However, alpha-lactalbumin could not be adsorbed onto the resin. alpha-Lactalbumin and beta-lactoglobulin from rennet whey could also be adsorbed and separated using a strong anion exchanger, quaternary aminoethyl-Toyopearl. The rennet whey was passed through a strong cation exchanger, sulphopropyl-Toyopearl, to separate lactoperoxidase and lactoferrin. alpha-Lactalbumin and beta-lactoglobulin were adsorbed onto quaternary aminoethyl-Toyopearl. alpha-Lactalbumin was eluted using a linear (0-0.15 M) concentration gradient of NaCl in 0.05 M Tris-HCl buffer (pH 8.5). Subsequently, beta-lactoglobulin B and beta-lactoglobulin A were eluted from the column with 0.05 M Tris-HCl (pH 6.8), using a linear (0.1-0.25 M) concentration gradient of NaCl. The yields were 1260 mg alpha-lactalbumin, 1290 mg beta-lactoglobulin B and 2280 mg beta-lactoglobulin A from 1 l rennet whey.

Animals↗
PubMed1987

beta-Lactoglobulin identified in marsupial milk. The primary structure, binding site and possible function of beta-lactoglobulin from eastern grey kangaroo (Macropus giganteus).

beta-Lactoglobulin has been isolated in the milk of the Eastern Grey Kangaroo (Macropus giganteus). This is the first time this protein has been reported to be in the milk of marsupials. The complete amino-acid sequence has been determined by spinning cup and pulsed liquid phase microsequencing of the protein and peptides after enzymatic or cyanogen bromide cleavages. The 155-residue protein is the shortest beta-lactoglobulin so far sequenced. When the kangaroo protein is included in a comparison of the members of the beta-lactoglobulin family, the percentage of residues common to all members is reduced from 33% to 13%. Despite the large number of accumulated amino-acid exchanges the protein exists as a dimer and shows higher homology to the usually very conservative dimeric, ruminant beta-lactoglobulins than to the monomeric protein from monogastrics. Half-cystine residues that form disulphide bridges are conserved. The Eastern Grey Kangaroo beta-lactoglobulin possesses significant homology in several characteristic segments thought to be important for a functional trait common to the beta-lactoglobulin family and retinol-binding proteins. Structural similarity to the retinol-binding protein is indicated by 22% of identical residues. Homology to the beta-lactoglobulins and retinol-binding proteins, the binding site and possible function based on comparative structural studies are discussed.

Amino Acid Sequence↗
PubMed1979

Immunochemical studies on beta-lactoglobulins. precipitin reactions of sow's and mare's mammary secretions against anti - bovine beta - lactoglobulin antiserum.

By double diffusion in agarose gel, in well defined experimental conditions, cross reactions were observed between porcine beta-lactoglobulins and anti-bovine beta-lactoglobulin antisera. The immunological reactivity between these beta-lactoglobulins from a monogastric and the ruminant anti beta-lactoglobulin antiserum thus implies a certain degree of similarity between the monomeric beta-lactoglobulins examined and the dimeric of the ruminants. With the same antisera it also proved possible to demonstrate the presence of beta-lactoglobulins in the mammary secretions of another monogastric, namely, the mare. Identity reactions observed between sow's and mare's beta-lactoglobulins seem to indicate a close similarity in their structures.

Animals↗
PubMed1991

The complete amino acid sequence of feline beta-lactoglobulin II and a partial revision of the equine beta-lactoglobulin II sequence.

The amino acid sequence of feline beta-lactoglobulin (designated II) has been determined. The protein chain is 163 amino acids long with a relative molecular mass of 18,558. The primary structure was determined by sequencing of native protein (residues 1-25), BPNS-skatole cleavage fragments and the peptides obtained by proteolytic cleavage with V8 proteinase and TPCK-trypsin. Feline beta-lactoglobulin II has 53 and 57% positional identities with bovine beta-lactoglobulin A and equine beta-lactoglobulin I, respectively, and approx. 68% with a revised sequence of equine beta-lactoglobulin II. The equine beta-lactoglobulin II sequence was re-examined between positions 78 and 122 resulting in a major revision in this area with only a single insertion to give a total of 163 residues.

Amino Acid Sequence↗
PubMed1994

13C-n.m.r. of the cyanylated beta-lactoglobulins: evidence that Cys-121 provides the thiol group of beta-lactoglobulins A and B.

The thiol groups of beta-lactoglobulins A and B have been cyanylated using [13C]KCN. The samples of [cyanato-13C]-cyanylated-beta-lactoglobulins A and B which we prepared had signals at 109.7 p.p.m. and 114.4 p.p.m. We conclude that the thiocyanate carbon having a chemical shift of 109.7 p.p.m. is in an apolar environment similar to a cyclohexane solvent, whereas the thiocyanate carbon having a chemical shift of 114.4 p.p.m. is in a polar environment similar to water. The signals with chemical shifts of 109.7 p.p.m. are assigned to the thiocyanate carbons of the native [cyanato-13C]cyanylated-beta-lactoglobulins A and B. We deduce that the signal at 114.4 p.p.m. is due to an irreversibly denatured/unfolded species produced by alkaline denaturation, which is caused by intramolecular thiol/disulphide exchange occurring during our cyanylation procedure. We propose that Cys-119 is cyanylated in the irreversibly denatured species and Cys-121 is cyanylated in the native [cyanato-13C]cyanylated-beta-lactoglobulins A and B. We suggest that the same intramolecular thiol-disulphide exchange reactions occurred when McKenzie and co-workers [McKenzie, Ralston and Shaw (1972) Biochemistry 11, 4539-4547] alkylated beta-lactoglobulins with iodoacetamide. Therefore the one mol of thiol/mol of monomer in the native beta-lactoglobulins is due to the thiol of Cys-121 and is not due to an equimolar mixture of Cys-119 and Cys-121 as they suggested.

Animals↗
PubMed2006

Irreversible thermal denaturation of beta-lactoglobulin retards adsorption of carrageenan onto beta-lactoglobulin-coated droplets.

The influence of isothermal heat treatments on the adsorption of anionic carrageenan molecules to the surfaces of anionic beta-lactoglobulin-coated droplets has been investigated. The zeta-potential, mean particle diameter, microstructure, and creaming stability of emulsions containing beta-lactoglobulin-coated droplets and/or carrageenan molecules that had previously been heat treated at temperatures ranging from 30 to 90 degrees C for 20 min were measured (pH 6.0, 150 mM NaCl). Three different heat treatments were used to establish the physicochemical origin of the influence of thermal history on the adsorption of carrageenan molecules to the protein coated droplets: (i) droplets and carrageenan were mixed at room temperature, then heated together; (ii) droplets were heated, cooled to room temperature, then mixed with carrageenan; (iii) carrageenan was heated, cooled to room temperature, then mixed with droplets. For treatments i and ii appreciably more carrageenan adsorbed to the protein-coated droplet surfaces at temperatures < or = 60 degrees C than at higher temperatures. For treatment iii, carrageenan adsorbed to the droplet surfaces across the whole temperature range. These results suggest that an irreversible thermal denaturation of the adsorbed beta-lactoglobulin molecules inhibited the adsorption of carrageenan molecules to the droplet surfaces. We postulate that there is a patch of positive charge on the surface of the native globular protein molecules which becomes more diffuse upon thermal denaturation. We found that the carrageenan molecules were unable to protect the beta-lactoglobulin-coated droplets at high temperatures (T > 60 degrees C) because they desorbed from the droplet surfaces. Nevertheless, adsorption of iota-carrageenan was capable of protecting the droplets against flocculation caused by surface denaturation of the adsorbed proteins at lower temperatures (T < or = 50 degrees C).

Adsorption↗
PubMed1990

Genetic variants of bovine beta-lactoglobulin. A novel wild-type beta-lactoglobulin W and its primary sequence.

A novel bovine beta-lactoglobulin W has been isolated and its complete primary structure is presented. It was isolated by chromatofocusing of a beta-lactoglobulin AW heterozygote and purified by recrystallization. During sequencing of the oxidized protein, it became evident that the new beta-lactoglobulin W is a subtype of variant B with a single difference at position 56. This Ile----Leu substitution, which means a shift of a methyl group from C-beta to C-gamma of the amino-acid side chain causes a change of pI of 0.007 units, which can be detected by high resolution electrophoresis. This Ile56 amino-acid residue is among the most conserved residues with the exception of kangaroo beta-LG. The structures of other bovine beta-lactoglobulins and their relationships are discussed.

Amino Acid Sequence↗
PubMed1989

Anti-bovine beta-lactoglobulin antibodies react with a human lactoferrin fragment and bovine beta-lactoglobulin present in human milk.

Human milk samples react against anti-bovine beta-lactoglobulin rabbit antibodies, as measured by a competitive radioimmunoassay. Immunoreactivity was positive even in milk from mothers consuming a diet free of cow's milk. An increase with a diet rich in cow's milk proteins was detected by immunoelectrophoresis. The human milk fraction cross-reacting with anti-bovine beta-lactoglobulin antibodies corresponds to the 20 kDa fragment from the N-terminal end of human lactoferrin. Three regions of this fragment exhibit sequence homology with a sequence contained in cow's beta-lactoglobulin (between residues 124 and 141).

Amino Acid Sequence↗
PubMed1994

Prevention of allergic sensitization to beta-lactoglobulin with conjugates made of beta-lactoglobulin coupled to isologous immunoglobulin G.

We have shown that, under certain conditions, a single dose of a conjugate of beta-lactoglobulin linked to isologous IgG suppresses specific antibody responses (IgE, IgG, and IgA) in rats immunized with beta-lactoglobulin. This suppression is allergen specific. It also appears to be effective when animals are first immunized and then tolerized. In addition, administration of the beta-lactoglobulin-IgG tolerogen abolishes mast cell mediator release. This has been shown both in vivo and with passively sensitized mast cells in vitro. We propose that the construction of a tolerogen made of whole protein allergen linked to IgG could provide a novel specific therapy for allergic reactions.

Animals↗
PubMed1995

Developmental regulation of the ovine beta-lactoglobulin/human serum albumin transgene is distinct from that of the beta-lactoglobulin and the endogenous beta-casein genes in the mammary gland of transgenic mice.

We compared the developmental pattern of expression of the sheep beta-lactoglobulin (BLG), the chimeric BLG/human serum albumin (HSA), and the endogenous murine beta-casein genes in the mammary gland of virgin, pregnant and lactating transgenic mice, both at the RNA (expression) and protein (synthesis and secretion) levels. The BLG and casein genes were expressed at very low levels in virgin animals and during early stages of pregnancy. The increase in the expression of these genes started at the second half of pregnancy and reached a peak between the end of pregnancy and day 10 of lactation. The accumulation of their RNA coincided with that of the corresponding proteins, indicating a transcriptional control of expression of these genes. The expression and secretion patterns of the endogenous casein gene in transgenic and nontransgenic mice were indistinguishable. The hybrid BLG/HSA gene constructs displayed distinct patterns of expression in virgin animals and at early stage of pregnancy, from that of the BLG transgene or the endogenous mouse milk protein gene. High levels of expression (17-60% of that on day 18 of pregnancy) were detected in the mammary gland of virgin animals. At day 5 of pregnancy there was a dramatic decrease in HSA synthesis and secretion in all transgenic strains tested. The down-regulation, revealed by immunoprecipitation and immunohistochemical studies, demonstrated that at that stage of pregnancy only 10-18% of ductal structures contained HSA expressing cells in contrast to the majority of ducts expressing HSA in virgin animals. These morphological studies also demonstrated that the down-regulation in HSA synthesis and secretion was correlated with the transition from ducts comprised of a single layer of epithelial cells (characteristic of the virgin state) to ducts composed of multilayers of such cells. In two of the three transgenic strains tested, the down-regulation at the protein level was associated with a similar decrease in HSA transcripts. In the exceptional strain no. 23, HSA transcripts continued accumulating even at this stage. The differences in the control of expression at the RNA level between these transgenic strains were also confirmed by in situ hybridization. Our results suggest the involvement of at least two regulatory mechanisms effective at early stages of gestation in the control of expression/secretion of the HSA transgene targeted for expression in the mammary gland by the BLG milk protein promoter. These putative mechanisms may play key roles in the interplay between normal mammogenesis and lactogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1996

Modification of the single unpaired sulfhydryl group of beta-lactoglobulin under high pressure and the role of intermolecular S-S exchange in the pressure denaturation [single SH of beta-lactoglobulin and pressure denaturation].

Chemical modification reactions of the unpaired sulfhydryl group of beta-lactoglobulin (LG) under high pressure and the role of this group in the pressure-induced denaturation were investigated. When LG was incubated at 400 MPa (pH 6.8) for 1 h, dimerization through intermolecular reaction of SH was observed. The generation of the covalently linked dimers were prevented by the presence of N-ethylmaleimide (NEM), an agent for SH-specific modification. The reactivity of the SH group of LG, which is buried inside in its native state, was increased by high pressure, as a result of its exposure to the protein surface accompanied by the pressure denaturation. The effect of NEM was also observed in the fluorescence change caused by high pressure, in both the intrinsic fluorescence of LG and the retinol fluorescence of the LG-retinol complex. The control showed an irreversible change at neutral pH, but it became mostly reversible in the presence of NEM. Compatible results were obtained by CD spectroscopy. Inter- and intramolecular reactions of the SH group are suggested to be main causes for the pressure-induced irreversible denaturation of LG.

Circular Dichroism↗
PubMed1997

Effect of saponin on the transmucosal passage of beta-lactoglobulin across the proximal small intestine of normal and beta-lactoglobulin-sensitised rats.

The ability of saponins and glycoalkaloids to permeabilise the mammalian intestinal barrier has been previously demonstrated in vitro, leading to the hypothesis that membranolytic saponins may facilitate transfer to the tissues of otherwise excluded macromolecules. An enhanced uptake of, for instance, potentially allergenic species from the lumen is one of the factors that may affect the induction of food allergy, and its presentation in already sensitised individuals. In the experiments described here, an increase in the transmucosal uptake of the milk allergen beta-lactoglobulin (beta LG) was assessed in non-sensitised and sensitised Brown Norway rats in the presence of Gypsophila saponin. Isolated jejunal loops were exposed in vivo to either beta LG followed by saponin, saponin followed by beta LG or the two compounds simultaneously. Portal vein blood samples were collected and assayed for beta LG and rat mucosal mast cell protease (RCMP II) activity. Mucosal tissue was also examined histologically and assayed for histamine content. Sham-operated animals, exposed to physiological buffer alone, were included as controls and beta LG measurements corrected for this component which was negligible. No transfer of beta LG occurred in the absence of saponin in non-sensitised rats, whereas a significant enhancement was observed in the presence of saponin. beta LG was detected in the portal circulation of sensitised rats exposed to beta LG alone; however addition of saponin to the intestinal lumen further enhanced this uptake, possibly by an independent mechanism. Histological examination of the mucosal epithelium exposed to saponin revealed damage, especially at the villus tips. Mucosal histamine and serum RCMP II concentrations were consistent with the differences observed between sensitised and non-sensitised animals. It is concluded that exposure to food constituents capable of permeabilising the mucosal epithelium may increase the risk of sensitisation to dietary antigens.

Animals↗