Interaction of alpha-lactalbumin with Cu2+.
It has been shown by intrinsic fluorescence spectroscopy that alpha-lactalbumin has several Cu2+ -binding sites per molecule. The Ca2+ -loaded protein binds two or more Cu2+ per molecule with an association constant of about 3 X 10(3) M-1. Apo-alpha-lactalbumin binds one Cu2+ per molecule with association constant 8 X 10(4) M-1 and from two to three Cu2+ with an association constant of about 4 X 10(3) M-1. The results obtained from spectrofluorometric pH titration of alpha-lactalbumin in the acidic pH region show the possible involvement of histidine residues in the coordination of Cu2+. The binding of Cu2+ to alpha-lactalbumin lowers significantly its thermostability and stability towards urea denaturation. The stability of Cu2+, Ca2+-alpha-lactalbumin against thermal and urea denaturation is similar to that of the apo protein. The thermal transition in Cu2+, Ca2+-alpha-lactalbumin occurs within the region of physiological temperatures which may suggest the existence of some thermal regulation of its functioning in vivo.
Permyakov
E A
EA
Institut of Biological Physics, U.S.S.R. Academy of Sciences, Pushchino, Moscow Region.
Morozova
L A
LA
Kalinichenko
L P
LP
Derezhkov VYu
D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007768:Lactalbumin / Q000378:metabolism*; D011485:Protein Binding; D011489:Protein Denaturation; D013050:Spectrometry, Fluorescence / Q000379:methods; D013816:Thermodynamics; D014508:Urea / Q000494:pharmacology
D014508:Urea; D007768:Lactalbumin; D002118:Calcium