Binding of Mg2+ to beta-casein A1: A multinuclear magnetic resonance study

N. Wahlgren, P. Dejmek, Torbjörn Drakenberg

Research output: Contribution to journalArticleScientificpeer-review

16 Citations (Scopus)

Abstract

25Mg, 43Ca and 31P NMR have been used to study the binding of Mg2+ and Ca2+ ions to β-casein A1. The concentration dependence of the line width of the 25Mg NMR signal shows that β-casein contains at least two different types of binding sites for Mg2+ ions, one with strongly bound, slowly exchanging ions and one with more weakly bound ions which undergo fast exchange.
The strong Mg2+ binding site has an unexpectedly high binding constant, Kbstrong 104 M–1, which has not been reported earlier. Mg2+ and Ca2+ compete for the Ca2+ binding sites of β-casein, while Na+ does not compete for these binding sites under physiological conditions.
The dependence of the 43Ca NMR chemical shifts on total concentration of Mg2+ and Ca2+, in the presence of β-casein, could be equally well fitted with a model assuming up to five identical and independent sites as with a model assuming five or more sites with negative cooperativity.
The proton dissociation constant, pka, for the strongest Ca2+ binding site was found to be 7·1.
Original languageEnglish
Pages (from-to)65-78
JournalJournal of Dairy Research
Volume60
Issue number1
DOIs
Publication statusPublished - 1993
MoE publication typeA1 Journal article-refereed

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beta-casein
Caseins
binding sites
Magnetic Resonance Spectroscopy
Binding Sites
casein
calcium
Ions
ions
protons
Protons

Cite this

Wahlgren, N. ; Dejmek, P. ; Drakenberg, Torbjörn. / Binding of Mg2+ to beta-casein A1 : A multinuclear magnetic resonance study. In: Journal of Dairy Research. 1993 ; Vol. 60, No. 1. pp. 65-78.
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abstract = "25Mg, 43Ca and 31P NMR have been used to study the binding of Mg2+ and Ca2+ ions to β-casein A1. The concentration dependence of the line width of the 25Mg NMR signal shows that β-casein contains at least two different types of binding sites for Mg2+ ions, one with strongly bound, slowly exchanging ions and one with more weakly bound ions which undergo fast exchange. The strong Mg2+ binding site has an unexpectedly high binding constant, Kbstrong 104 M–1, which has not been reported earlier. Mg2+ and Ca2+ compete for the Ca2+ binding sites of β-casein, while Na+ does not compete for these binding sites under physiological conditions. The dependence of the 43Ca NMR chemical shifts on total concentration of Mg2+ and Ca2+, in the presence of β-casein, could be equally well fitted with a model assuming up to five identical and independent sites as with a model assuming five or more sites with negative cooperativity. The proton dissociation constant, pka, for the strongest Ca2+ binding site was found to be 7·1.",
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Binding of Mg2+ to beta-casein A1 : A multinuclear magnetic resonance study. / Wahlgren, N.; Dejmek, P.; Drakenberg, Torbjörn.

In: Journal of Dairy Research, Vol. 60, No. 1, 1993, p. 65-78.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Binding of Mg2+ to beta-casein A1

T2 - A multinuclear magnetic resonance study

AU - Wahlgren, N.

AU - Dejmek, P.

AU - Drakenberg, Torbjörn

PY - 1993

Y1 - 1993

N2 - 25Mg, 43Ca and 31P NMR have been used to study the binding of Mg2+ and Ca2+ ions to β-casein A1. The concentration dependence of the line width of the 25Mg NMR signal shows that β-casein contains at least two different types of binding sites for Mg2+ ions, one with strongly bound, slowly exchanging ions and one with more weakly bound ions which undergo fast exchange. The strong Mg2+ binding site has an unexpectedly high binding constant, Kbstrong 104 M–1, which has not been reported earlier. Mg2+ and Ca2+ compete for the Ca2+ binding sites of β-casein, while Na+ does not compete for these binding sites under physiological conditions. The dependence of the 43Ca NMR chemical shifts on total concentration of Mg2+ and Ca2+, in the presence of β-casein, could be equally well fitted with a model assuming up to five identical and independent sites as with a model assuming five or more sites with negative cooperativity. The proton dissociation constant, pka, for the strongest Ca2+ binding site was found to be 7·1.

AB - 25Mg, 43Ca and 31P NMR have been used to study the binding of Mg2+ and Ca2+ ions to β-casein A1. The concentration dependence of the line width of the 25Mg NMR signal shows that β-casein contains at least two different types of binding sites for Mg2+ ions, one with strongly bound, slowly exchanging ions and one with more weakly bound ions which undergo fast exchange. The strong Mg2+ binding site has an unexpectedly high binding constant, Kbstrong 104 M–1, which has not been reported earlier. Mg2+ and Ca2+ compete for the Ca2+ binding sites of β-casein, while Na+ does not compete for these binding sites under physiological conditions. The dependence of the 43Ca NMR chemical shifts on total concentration of Mg2+ and Ca2+, in the presence of β-casein, could be equally well fitted with a model assuming up to five identical and independent sites as with a model assuming five or more sites with negative cooperativity. The proton dissociation constant, pka, for the strongest Ca2+ binding site was found to be 7·1.

U2 - 10.1017/S0022029900027357

DO - 10.1017/S0022029900027357

M3 - Article

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EP - 78

JO - Journal of Dairy Research

JF - Journal of Dairy Research

SN - 0022-0299

IS - 1

ER -