Heat-induced secondary structure and conformation change of bovine serum albumin investigated by Fourier transform infrared spectroscopy.
Fourier transform infrared (FT-IR) spectra were measured for an aqueous solution (pD = 5.40) of defatted monomer bovine serum albumin (BSA) over a temperature range of 25-90 degrees C to investigate temperature-induced secondary structure and conformation changes. The curve fitting method combined with the Fourier self-deconvolution technique allowed us to explore details of the secondary structure and conformation changes in defatted BSA. Particularly striking in the FT-IR spectra was an observation of the formation of an irreversible intermolecular beta-sheet of BSA on heating above 70 degrees C. A band at 1630 cm(-1) in the spectra was assigned to short-segment chains connecting alpha-helical segments. The transition temperature for the short-segment chains connecting alpha-helical segments is lower by 17-18 degrees C, when compared to those of the alpha-helix, turn, and intermolecular beta-sheet structures of BSA, suggesting that the alpha-helix and turn structures of BSA are cooperatively denatured on heating. Moreover, the results give an important feature in heat-induced denaturation of BSA that the conformation changes occur twice around both 57 and 75 degrees C. The appearance of two peaks is interpreted by the collapse of the N-terminal BSA domain due to the crevice in the vicinity between domains I and II at low-temperature transition and by the change in cooperative unit composed of the other two BSA domains at high-temperature transition.
Murayama
Koichi
K
Department of Biochemistry and Biophysics, Graduate School of Medicine, Gifu University, 1-1, Yanagido, Gifu 501-1194, Japan. mkoichi@cc.gifu-u.ac.jp
Tomida
Mihoko
M
D000818:Animals; D002417:Cattle; D006358:Hot Temperature; D044367:Phase Transition; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods / Q000706:statistics & numerical data; D013696:Temperature
D012710:Serum Albumin, Bovine