Effect of Heat Treatment on the Conformation and Aggregation of β-Lactoglobulin A, B, and C

Manderson, Gavin A.; Hardman, Michael J.; Creamer, Lawrence K.

doi:10.1021/jf980515y

Cited by 169 publications

(179 citation statements)

References 53 publications

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“…Concentrations of (V, P-> *-, and y-casein, oclactalbumin, and P-lactoglobulin were determined by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis according to the method of Manderson et al (1998), with the following differences. Resolving gels were made from a mixture of 48.5 g of a 30% stock solution of a 37.5:1 mixture of acrylamide and N,N'-methylenebis (acrylamide), 23 g of resolving gel buffer (1.5 M Tris adjusted (at 20°C) to apH of 8.8), and 10 g of distilled, deionised water (DDW).…”

Section: Milk Analysesmentioning

confidence: 99%

Variation in the composition of milk protein from pasture‐fed dairy cows in late lactation and the effect of grain and silage supplementation

Mackle¹,

Bryant²,

Petch³

et al. 1999

New Zealand Journal of Agricultural Research

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Sources of variation in milk protein composition were determined after approximately 203 days-in-milk for spring-calving Friesian cows grazing ryegrass-white clover pastures in New Zealand. Three groups each of 15 multiparous cows were managed as separate herds. Each herd was subjected to one of three management strategies: pasture only, pasture supplemented with 2-3 kg cow 1 d -1 maize grain, and pasture plus 5-6 kg cow -1 d -1 maize grain and 3-4 kg cow -1 d -1 pasture silage. During a 3-week period beginning in February 1994, milk samples were collected twiceweekly from individual cows and the detailed protein composition determined. Variation was observed in milk yield and the concentrations of all protein components measured, with betweencow variation being greater than within-cow variation for all parameters except non-protein N and urea. Supplementing pasture with maize grain and/or silage increased milk yield but had only minor effects on protein composition. These data will enable increased efficiency of experimental design in this research area, and provide details of the natural variation in milk protein composition. This variation gives an indication of the extent that *Author for correspondence A98046 Received 9 September 1998; accepted 7 April 1999 milk protein composition could be manipulated by on-farm practices, or through the selection of cows with defined milk protein profiles.

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Section: Milk Analysesmentioning

confidence: 99%

Variation in the composition of milk protein from pasture‐fed dairy cows in late lactation and the effect of grain and silage supplementation

Mackle¹,

Bryant²,

Petch³

et al. 1999

New Zealand Journal of Agricultural Research

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“…At pH above 7.1 this loop is folded back to reveal the interior of the calyx. In this paper the structure of variant B at pH 7.1 is presented and compared with the structures of variant A at pH 6.2, pH 7.1, and pH 8.2 for additional insight into the structural basis of the Tanford transition and for insight into altered functionality of variants A and B of bovine BLG~Hill et al, 1996;Manderson et al, 1998!. Although preliminary results have been reported on the structures of BLGA, BLGB, and BLGC in lattice Y~Bewley et al, 1997!, the N-and C-terminal regions and several critical loops are very poorly defined.…”

mentioning

confidence: 99%

Functional implications of structural differences between variants A and B of bovine β‐lactoglobulin

Qin

Bewley

Creamer³

et al. 1999

Protein Science

136

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The structure of the trigonal crystal form of bovine b-lactoglobulin variant B at pH 7.1 has been determined by X-ray diffraction methods at a resolution of 2.22 Å and refined to values for R and R free of 0.239 and 0.286, respectively. By comparison with the structure of the trigonal crystal form of bovine b-lactoglobulin variant A at pH 7.1, which was determined previously @Qin BY et al., 1998, Biochemistry 37:14014-14023#, the structural consequences of the sequence differences D64G and V118A of variants A and B, respectively, have been investigated. Only minor differences in the core calyx structure occur. In the vicinity of the mutation site D64G on loop CD~residues 61-67!, there are small changes in main-chain conformation, whereas the substitution V118A on b-strand H is unaccompanied by changes in the surrounding structure, thereby creating a void volume and weakened hydrophobic interactions with a consequent loss of thermal stability relative to variant A. A conformational difference is found for the loop EF, implicated in the pH-dependent conformational change known as the Tanford transition, but it is not clear whether this reflects differences intrinsic to the variants in solution or differences in crystallization.Keywords: bovine b-lactoglobulin; crystal structure; genetic variants; hydrophobic stabilization Bovine b-lactoglobulin~BLG!, the major whey protein of cow's milk at a concentration of 0.3 g0100 mL~Bell & McKenzie, 1964!, was first isolated by Palmer~1934!. Mature bovine b-lactoglobulin has 162 residues, and is a member of the lipocalin protein superfamily~Flower, 1994, 1996!. Members of this family have a distinctive eight-stranded b-barrel structure, the central cavity of which binds a variety of hydrophobic molecules~Banaszak et al., 1994!. In the case of BLG, the primary site for fatty-acid binding has recently been established crystallographically to be inside this cavity~Qin et al., 1998b; Wu et al., 1999!. The structure of BLG is now reliably known following two independent redeterminations of the structure in the triclinic~lattice X!~Brownlow et al., 1997! and orthorhombic~lattice Y! forms~Bewley et al., 1997!. The latter structure has led to our redetermination of the structure in the trigonal~lattice Z! form~Qin et al., 1998a!. In lattice Z, in contrast to lattices X and Y, the entire molecule is well defined from electron density maps.Three variants of BLG, labeled as A, B, and C, commonly occur in cow's milk. Variants A and B~BLGA and BLGB! differ at two sites: Asp64 in A is changed to Gly in B, and Val118 in A is changed to Ala in B. Variants B and C differ at one site: Gln59 in B is changed to His in C. Thus, the isoelectric points for variants A, B, and C differ slightly: pI ϭ 5.26, 5.34, and 5.33, respectively, in 0.1 M KCl at room temperature~McKenzie, 1971!. Of technological significance, bovine BLG variants have different effects on the industrial processing of milk and on the characteristics of milk products~Hill et al., 1996!. Thermal stability is in the order B ...

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“…They postulated the prominent role of disulphide bonds. Other authors supported the view that b-Lg aggregates through a series of parallel and consecutive steps which involve both covalent (thiol/disulphide bond interchanges) and noncovalent (hydrophobically driven associations) reactions [18]. The relative proportion of these two types of interactions seems to be highly temperature-dependent.…”

Section: Nature Of Stabilising Forces Involved In Formed Aggregatesmentioning

confidence: 87%

“…In earlier studies, the formation of heatinduced disulphide-bonded dimers as intermediates was reported to be an important step in the further aggregation of b-Lg [18,22]. The presence of these intermediates at tg was determined under different protein and mineral environments.…”

Section: Formation Of B -Lg Covalent Dimersmentioning

confidence: 99%

Mineral modulation of thermal aggregation and gelation of whey proteins: from ?-lactoglobulin model system to whey protein isolate

Caussin

Famelart

Maubois

et al. 2003

Lait

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-Solutions of 100 g·kg -1 of b-lactoglobulin (b-Lg), b-Lg + a-lactalbumin (a-La), b-Lg + a-La + bovine serum albumin (BSA) or whey protein isolate (WPI) were heated at 75°C, pH 6.8 in water and in the presence of either 100 mmol·L -1 NaCl or 10 mmol·L -1 CaCl 2 . The subsequent polymerisation-aggregation processes in solution before gelation and the physical properties of the formed gels were determined. The disappearance of native-like proteins, formation of b-Lg covalent dimer and the nature of the interactions involved in the formed aggregates were addressed. Whatever the protein system, both NaCl and CaCl 2 increased gel strength and decreased gelation time. At gelling time, relatively small aggregates, formed by the contribution of the total initial amount of proteins, were observed in samples without added salts. In contrast, with NaCl or CaCl 2 , only part of the initial amount of proteins was aggregated before gel time. Very large aggregates were formed in the presence of calcium. Under these two mineral conditions, as well as in samples without added salt, covalent disulphide bonds were seen to be the major forces involved in the aggregation process at gel time.Whey protein / aggregation / gelation / calcium / sodium Résumé -Modulation de l'agrégation et de la gélification des protéines de lactosérum par les minéraux : de la b-lactoglobuline pure à l'isolat de protéines sériques. Des gels de différentes solutions de protéines (b-lactoglobuline (b-Lg), b-Lg + a-lactalbumine (a-La), b-Lg + a-La + sérum albumine bovine (BSA), isolat de protéines sériques) à 100 g·kg -1 étaient formés à pH 6.8 dans l'eau ou dans 100 mmol·L -1 NaCl ou 10 mmol·L -1 CaCl 2 . Les propriétés physiques des gels ainsi que les réactions d'agrégation des protéines (disparition des protéines natives, formation de dimères covalents de b-Lg et nature des liaisons entre protéines agrégées) ont été étudiées. Le NaCl et le CaCl 2 augmentent la force des gels et diminuent les temps de gel (tg). Au tg, sans ajout de sels, les agrégats formés, de petites tailles, impliquent la totalité des protéines présentes en solution. En revanche, en présence de NaCl ou de CaCl 2 , seule une partie des protéines est impliquée dans la formation des agrégats au tg. La taille des agrégats formés est plus élevée en présence de CaCl 2 . Dans toutes les conditions, les ponts disulfures interprotéiques semblent être les liaisons majoritairement impliquées dans la formation des agrégats au tg.Protéine de lactosérum / agrégation / gélification / calcium / sodium * Corresponding author: sbouhal@rennes.inra.fr 2 F. Caussin et al.

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Effect of Heat Treatment on the Conformation and Aggregation of β-Lactoglobulin A, B, and C

Cited by 169 publications

References 53 publications

Variation in the composition of milk protein from pasture‐fed dairy cows in late lactation and the effect of grain and silage supplementation

Variation in the composition of milk protein from pasture‐fed dairy cows in late lactation and the effect of grain and silage supplementation

Functional implications of structural differences between variants A and B of bovine β‐lactoglobulin

Mineral modulation of thermal aggregation and gelation of whey proteins: from ?-lactoglobulin model system to whey protein isolate

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