Circular dichroic and 1H-NMR studies on the aged form of bovine plasma albumin.
Bovine plasma albumin (BPA) has 17 disulfide bonds and approximately one SH group at Cys-34 which catalyzes the intramolecular SH, S-S exchange reaction in the alkaline region at low ionic strength, resulting in the formation of the aged form (A-form). 1) Fractions of alpha-helix (f alpha) and beta-form (f beta) of iodoacetamide-blocked non-aged BPA (IA-BPA) at pH 6.5 (the N-form) and 9.0 (the B-form) in the absence of added salt were 0.70, 0.12 and 0.62, 0.18, respectively (Era et al. (1990]. However, there were no changes in f alpha and f beta of the iodoacetamide-blocked A-form (IA-A-form) over the pH range from 5.5 to 9.1 in the absence of added salt or in 0.10 M KCl (f alpha approximately 0.60, f beta approximately 0.20), indicating that the secondary structure of the IA-A-form might be similar to that of non-aged IA-BPA at pH 9.0 (B-form) in the absence of added salt, that is, the frozen B-form, stabilized covalently by the repairing of disulfide bonds. 2) The rigidity of the A- and IA-A-forms, as monitored by cross-relaxation times between irradiated and observed protein protons, was similar to or slightly higher than that of non-aged IA-BPA or BMA.(ABSTRACT TRUNCATED AT 250 WORDS)
Era
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S
Department of Physiology, School of Medicine, Gifu University, Japan.
Kuwata
K
K
Sogami
M
M
Kato
K
K
Watari
H
H
D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D003545:Cysteine / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D009994:Osmolar Concentration; D011487:Protein Conformation; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry
D004220:Disulfides; D013438:Sulfhydryl Compounds; D012710:Serum Albumin, Bovine; D006859:Hydrogen; D003545:Cysteine