[Binding of Mg ions with alpha-lactalbumin studied by fluorescent spectroscopy].
Titration of metal-freed bovine alpha-lactalbumin with Mg2+ ions causes a two-stepped decrease in the fluorescence quantum yield and a pronounced spectral shift towards shorter wavelengths. It seems to reflect conformational changes induced by the binding of two Mg2+ ions to the protein molecule which results in a transfer of some tryptophan residues from the protein surface into an interior part of the protein in rigid unpolar environment. The Mg2+ association constants evaluated from the fluorimetric Mg2+-titration are 2x10(3) and 2x10(2) M-1. Mg2+ ions in millimolar concentrations almost do not influence the binding of Ca2+ ions to protein. It is assumed that Ca2+ and Mg2+ ions are bound to different sites on alpha-lactalbumin. Mono-calcium, mono-magnesium, bi-magnesium and apo-forms of alpha-lactalbumin are distinct in their fluorescence properties which suggests the difference in the conformation of these forms. The binding of Ca2+ and Mg2+ ions to alpha-lactalbumin has to modulate its function.
D000818:Animals; D002118:Calcium; D002417:Cattle; D007768:Lactalbumin / Q000378:metabolism*; D008274:Magnesium; D011485:Protein Binding; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence / Q000379:methods
D007768:Lactalbumin; D008274:Magnesium; D002118:Calcium
Issledovanie sviazyvaniia ionov Mg al'fa-latal'buminom metodom fluorestsentnoĭ spektroskopii.