Proton relaxation rates of water in dilute solutions of β-lactoglobulin. Determination of cross relaxation and correlation with structural changes by the use of two genetic variants of a self-associating globular protein

Pessen, Helmut; Purcell, J. M.; Farrell, Harold M.

doi:10.1016/0167-4838(85)90002-0

“…In whey, α-lactalbumin exists as calcium metalloprotein and calcium is released below pH 4.0, making the molecule flexible with large structural changes accompanied by apparent denaturation (Oakenfull et al 1997). Residual β-lactoglobulin in paneer whey, when adjusted to a low pH (as in whey lemon beverage), is likely to form octomers, resulting in increased viscosity (Pessen et al 1985). Viscosity of whey proteins decreases near pI (Cayot and Lorient 1997) but there is slight increase towards acidic side of their pI as in the case of whey lemon beverage.…”

Section: Resultsmentioning

confidence: 99%

Assessment of stability of binary sweetener blend (aspartame x acesulfame-K) during storage in whey lemon beverage

Arora

¹

,

Shendurse

²

,

Sharma

³

et al. 2011

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In the present study, artificial sweeteners-aspartame, acesulfame-K and binary sweetener blend of aspartame x acesulfame-K were assessed for stability during storage in whey lemon beverage. A solid phase extraction method using C 18 cartridges was standardized for the isolation of aspartame, acesulfame-K and their degradation products in whey lemon beverage. HPLC analytical conditions were standardized over C 18 column for simultaneous separation of multiple sweeteners and their degradation products in sample isolates. Storage studies revealed that increase in acidity and viscosity and decrease in pH and ascorbic acid content of artificially sweetened whey lemon beverage samples were similar to the changes occurring in control samples during storage. Analysis using HPLC showed that aspartame (added either singly or in a blend) and acesulfame-K (added in a blend) were stable in whey lemon beverage under refrigerated condition for 15 days.

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“…These variants of bovine BLG have different self-association properties~Hill et al, 1996!. Variant A forms dimers and then octamers under increasingly acidic conditions, whereas variants B and C do not form octamers~Timasheff & Townend, 1961;Timasheff, 1964;Pessen et al, 1985!, but do form dimers, with dissociation constants in the micromolar range at pH ; 7 and stability constants in the order Reprint requests to: Geoffrey B. Jameson, Centre for Structural Biology, Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand; e-mail: g.b.jameson@massey.ac.nz; or Edward N. Baker, School of Biological Science, Auckland University, Private Bag 92-019, Auckland, New Zealand; e-mail: ted.baker@auckland.ac.nz.…”

Section: Introductionmentioning

confidence: 99%

“…These variants of bovine BLG have different self-association properties~Hill et al, 1996!. Variant A forms dimers and then octamers under increasingly acidic conditions, whereas variants B and C do not form octamers~Timasheff & Townend, 1961;Timasheff, 1964;Pessen et al, 1985!, but do form dimers, with dissociation constants in the micromolar range at pH ; 7 and stability constants in the order Reprint requests to: Geoffrey B. Jameson, Centre for Structural Biology, Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand; e-mail: g.b.jameson@massey.ac.nz; or Edward N. Baker, School of Biological Science, Auckland University, Private Bag 92-019, Auckland, New Zealand; e-mail: ted.baker@auckland.ac.nz.Abbreviations: BLG, b-lactoglobulin; BLGA, bovine b-lactoglobulin variant A; BLGB, bovine b-lactoglobulin variant B; BLGC, bovine b-lactoglobulin variant C; HEPES, N-~2-hydroxyethyl!piperazine-N9-2-ethanesulfonic acid! ; RMS, root-mean-square; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; TAPSO, 3-@N-tris~hydroxymethyl!methylamino#-2-hydroxypropanesulfonic acid.…”

mentioning

confidence: 99%

“…These variants of bovine BLG have different self-association properties~Hill et al, 1996!. Variant A forms dimers and then octamers under increasingly acidic conditions, whereas variants B and C do not form octamers~Timasheff & Townend, 1961;Timasheff, 1964;Pessen et al, 1985!, but do form dimers, with dissociation constants in the micromolar range at pH ; 7 and stability constants in the order C Ͼ Ͼ B Ͼ A~Timasheff & Townend, 1961;McKenzie, 1971;McKenzie & Sawyer, 1972;Thresher et al, 1994;Hill et al, 1996;Thresher & Hill, 1997!. Both bovine BLG variants A and B undergo pH-dependent conformational changes in the range pH 6.5 to pH 7.5, the so called N ? R or Tanford transition~Tanford et al, 1959;Hambling et al, 1994!.…”

mentioning

confidence: 99%

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

Qin

¹

,

Bewley

²

,

Creamer³

et al. 1999

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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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“…Cette protéine n'a pas été utilisée à notre connaissance pour la supplémentation des milieux de culture. -modification de la conformation en fonction du pH du milieu : au-dessus de pH 6,8 (les milieux de culture sont tamponnés à pH 7,2), la molécule subit une transition particulière (Pessen et al, 1985), qui entraîne le démasquage d'un groupement carboxylique et la réactivité du groupement SH 121 (Georges et al, 1962;Timasheff et al, 1966;Mc Kenzie et Sawyer, 1967;Tandford, 1968Tandford, et 1970McKenzie, 1971);16 Tableau Il. Sécrétion d'anticorps monoclonaux (hybridome Mark 3; mg/I) en fonction de la concentration en sérum de veau foetal.…”

Section: Discussionunclassified

Rôle de la β-lactoglobuline dans l'activité proliférative du lactosérum

Moulti-Mati¹,

Mati²,

Capiaumont³

et al. 1991

Lait

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Proton relaxation rates of water in dilute solutions of β-lactoglobulin. Determination of cross relaxation and correlation with structural changes by the use of two genetic variants of a self-associating globular protein

Cited by 103 publications

References 34 publications

Assessment of stability of binary sweetener blend (aspartame x acesulfame-K) during storage in whey lemon beverage

Assessment of stability of binary sweetener blend (aspartame x acesulfame-K) during storage in whey lemon beverage

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

Rôle de la β-lactoglobuline dans l'activité proliférative du lactosérum

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