Studies on the interactions between purified bovine caseins and alkaline-earth-metal ions

Dickson, Ian; Perkins, D.J.

doi:10.1042/bj1240235

Cited by 120 publications

(80 citation statements)

References 20 publications

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“…The number of calcium binding sites determined at high ionie strength needs to be compared to the 4.6 and 3.4 sites respectively found by DICKSON and PERKINS (1971) (pH 7.4-11=0.10) and by IMADE et al (1977) (pH 6.9-11=0.07) ; the differences in the results may be due to the pH and ionie strength effects. Cu 2 + and Fe 2 + binding ability is not altered by ionie strength because of the presence of coordination links.…”

Section: Discussionmentioning

confidence: 99%

Effect of pH and ionic strength on the binding of bivalent cations to β-casein

Baumy

Brulé

1988

Lait

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SummaryThe binding capacity of (3-casein for Ca 2 +, Mg 2 +, Mn 2 +, Zn 2 +, Cu 2 +, Fe 2 + was studied at various pHs (from 8.00 to 5.00) and different ionie strengths (about 0, 0.05, 0.10).(3-casein can bind 7 bivalent cations atoms, at pH higher than 7.00 and low ionie strength, before precipitation occurs. For Ca 2 +, Mg +, Mn 2 +, Zn 2 + the binding ability decreases with pH or when ionie strength increases. For Cu 2 + and Fe 2 +, no effect of~H and ionie strength were detected. Affinity constants of (3-casein towards Ca 2 +, Mg +, Zn 2 + and Mn 2 + were investigated using SCATCHARD's plot at pH 6.60 and ionie strength = 0.10 ; it shows different kinds of binding sites (phosphoseryl, carboxylic) and different affinities for the cations corresponding to different kinds of links.Key words : (3-casein -Bivalent cations -Binding -pH -Ionie strength. Résumé Effet du pH et de la force ionique sur la fixation des cations bivalents par la caséine (3Une étude sur les capacités de fixation de la caséine (3 pour Ca 2 +, Mg 2 +, Mn 2 +, Zn 2 +, Cu 2 +, Fe 2 + a été réalisée à différents pH (de 8,00 à 5,00) et à différentes forces ioniques (0, 0,05, 0,10).A pH supérieur à 7,00 et à force ionique faible, la caséine~peut fixer jusqu'à 7 atomes de cations bivalents sans précipiter. Pour Ca 2 +, Mg 2 +, Mn + et Zn 2 + , ces capacités de fixation diminuent quand le pH chute ou quand la force ionique s'accroît. Ces deux caractéristiques du milieu n'ont pas d'influence sur la fixation du Cu 2 + et Fe 2 +. Les constantes d'affinité déterminées par la représentation de SCATC HARD de cette protéine vis-à-vis de Ca 2 +, Mg 2 +, Zn 2 + et Mn 2 + ont été déterminées à pH 6,60 et pour une force ionique de 0,10. Différents types de sites (phosphosériques et carboxyliques) ont été mis en évidence ; ils ont des affinités variables pour les cations et correspondent à différents types de liaison.

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Section: Discussionmentioning

confidence: 99%

Effect of pH and ionic strength on the binding of bivalent cations to β-casein

Baumy

Brulé

1988

Lait

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“…On the other hand, bovine κ-CN does not sequester ACP, it is not precipitated by calcium ions, even at high concentrations (Dickson and Perkins, 1971;Mekmene and Gaucheron, 2011, and it can stabilize the other calcium-sensitive caseins against precipitation by calcium ions (Waugh and Talbot, 1971). All milks contain an ortholog of κ-CN and, in the 6 examples where the composition of casein has been determined (Supplementary Table S1; http://dx.doi.org/10.3168/jds.2013-6831), the percentage of κ-CN in whole casein varies from less than 2% to more than 17% (Baranyi et al, 1995;Miranda et al, 2004;Boumahrou et al, 2009;Holt and Carver, 2012).…”

Section: Safe Secretion Of High Concentrations Of Potentially Fibrillmentioning

confidence: 93%

Invited review: Caseins and the casein micelle: Their biological functions, structures, and behavior in foods

Holt

Carver

Ecroyd

et al. 2013

Journal of Dairy Science

394

240

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A typical casein micelle contains thousands of casein molecules, most of which form thermodynamically stable complexes with nanoclusters of amorphous calcium phosphate. Like many other unfolded proteins, caseins have an actual or potential tendency to assemble into toxic amyloid fibrils, particularly at the high concentrations found in milk. Fibrils do not form in milk because an alternative aggregation pathway is followed that results in formation of the casein micelle. As a result of forming micelles, nutritious milk can be secreted and stored without causing either pathological calcification or amyloidosis of the mother's mammary tissue. The ability to sequester nanoclusters of amorphous calcium phosphate in a stable complex is not unique to caseins. It has been demonstrated using a number of noncasein secreted phosphoproteins and may be of general physiological importance in preventing calcification of other biofluids and soft tissues. Thus, competent noncasein phosphoproteins have similar patterns of phosphorylation and the same type of flexible, unfolded conformation as caseins. The ability to suppress amyloid fibril formation by forming an alternative amorphous aggregate is also not unique to caseins and underlies the action of molecular chaperones such as the small heat-shock proteins. The open structure of the protein matrix of casein micelles is fragile and easily perturbed by changes in its environment. Perturbations can cause the polypeptide chains to segregate into regions of greater and lesser density. As a result, the reliable determination of the native structure of casein micelles continues to be extremely challenging. The biological functions of caseins, such as their chaperone activity, are determined by their composition and flexible conformation and by how the casein polypeptide chains interact with each other. These same properties determine how caseins behave in the manufacture of many dairy products and how they can be used as functional ingredients in other foods. aBStraCtA typical casein micelle contains thousands of casein molecules, most of which form thermodynamically stable complexes with nanoclusters of amorphous calcium phosphate. Like many other unfolded proteins, caseins have an actual or potential tendency to assemble into toxic amyloid fibrils, particularly at the high concentrations found in milk. Fibrils do not form in milk because an alternative aggregation pathway is followed that results in formation of the casein micelle. As a result of forming micelles, nutritious milk can be secreted and stored without causing either pathological calcification or amyloidosis of the mother's mammary tissue. The ability to sequester nanoclusters of amorphous calcium phosphate in a stable complex is not unique to caseins. It has been demonstrated using a number of noncasein secreted phosphoproteins and may be of general physiological importance in preventing calcification of other biofluids and soft tissues. Thus, competent noncasein phosphoproteins have similar patterns of phosp...

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“…6, too. The steep shift of absorption band of -P0 3 z -was observed up to about 1 mM CaCI" and on the other hand an absorp- tion of --COO-at 1400 em-I decreased linearly up to about 3 mM CaC1 e , and then a slow decrease was observed above 3 mM. Thus, it seems that there are three steps in the interaction of calcium to calcium binding groups.…”

Section: Changes Of Absorption Bands With Calcium Concentrationmentioning

confidence: 91%

“…11 The extent of precipitation is affected by pH, ionic strength and temperature. 2 ) Dickson and Perkins 3 ) assumed from an analysis of calcium binding curve that calcium interacts predominantly with phosphate groups of u sl -easein at low concentration of calcium. Dalgleish 4 ) found a stepwise increase in the fluorescence of tryptophyl residues with an increase in calcium concentration.…”

mentioning

confidence: 99%