Differential scanning calorimetry of a metalloprotein under controlled metal-ion activity.
In order to investigate the thermodynamics of the unfolding of metalloproteins, the thermal denaturation of bovine alpha-lactalbumin (BLA), a typical calcium-binding protein, was investigated under a wide variety of calcium ion activities by means of differential scanning calorimetry. The excess heat capacity obtained as above is composed of those of the following three reactions: (i) the release of a calcium ion from holo-BLA; (ii) the capture of the released calcium ion by the chelating reagent; and (iii) the denaturation of native apo-BLA. The results indicated that the presence of the chelating reagent had a remarkable effect on the apparent enthalpy change for the denaturation of holo-BLA. On the other hand, the influence of the chelator on the heat capacity change was shown to be negligible. Because the denaturation reaction of holo-BLA includes Reactions (i) and (iii), it had to be handled as a three-state reaction. Such an investigation of the unfolding has been scarcely found that the activity of the metal ion is controlled precisely in wide range.
Yasui
Masanori
M
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan.
Miyahara
Taku
T
Aizawa
Tomoyasu
T
Demura
Makoto
M
Nitta
Katsutoshi
K
D000818:Animals; D002118:Calcium / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D002413:Cations, Divalent; D002417:Cattle; D002614:Chelating Agents / Q000737:chemistry; D007768:Lactalbumin / Q000737:chemistry*; D008667:Metalloproteins / Q000737:chemistry*; D011489:Protein Denaturation; D013816:Thermodynamics
D002413:Cations, Divalent; D002614:Chelating Agents; D008667:Metalloproteins; D007768:Lactalbumin; D002118:Calcium