Microheterogeneity of plasma albumins. V. Permutations in disulfide pairings as a probable source of microheterogeneity in bovine albumin

Evidence for Two Molecular Forms of Streptococcal Erythrogenic Toxin

“…The first one is that the heterogeneity of the protein is related to oxidation of sulfhydryl groups to disulfide bridges [23] or to differences in the pairing of half-cystine residues [22,25]. Thc second interpretation is that the protein can bind, by sulfhydryl groups, small molecules or other proteins [22,24,261. Our results fit better with the second hypothesis.…”

Comparative 1H NMR studies on the structural looseness of the aged (A) and non-aged (N) bovine mercaptalbumin in the alkaline region

“…The structural characteristics of the A-form of BMA have been studied by Foster's and Wallevik's groups using [␣] 233 [4,5], b 0 of the Moffitt-Yang equation [5], the CD-resolved secondary structure [18], the pH-solubility profile in 3.0 M KCl [3,4], titration of the 98 carboxylates and 17 histidines [5], the hydrodynamic volume [5,6,18], the tryptophyl fluorescence spectrum [5,8,19], the difference spectrum [5], the rotational correlation time of a labeled spin-probe [15,16], the kinetic analysis of the N ↔ A reaction [4,5,[8][9][10], the 1 H NMR cross-relaxation time (T IS ) between irradiated and observed protein protons in the absence of added salt [18] and the catabolic rates of the A-and N-forms in vivo [7].…”

“…The protein concentrations were determined with a Hitachi 320 spectrometer, assuming E(1%, 1 cm) of BMA, IA-BSA and IA-A-BMA at 279 nm to be 6.67. 3 Commercial BSA contains small amounts of proteolytic enzyme which catalyzes a very limited cleavage of BSA in the F-form near pH 3.8, resulting in the formation of partially hydrolyzed BSA (BSA * and BSA ** ) [38]. The mixture of BSA * (66 kDa), BSA ** (∼63 kDa), and BSA (66 kDa) has a tendency to form a transparent gel above 7% and a viscous solution below 5% in D2O at pD 4.0 (pD range of the F-form), though highly purified proteolytic enzyme-free BMA, prepared according to the Hagenmaier and Foster method [14], is a transparent solution at pD 4.0 even at 12% after 5 days incubation at 35 • C [24,25,39].…”

“…It has been reported by many groups [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] that the intramolecular SH, S-S exchange reaction of BMA in the alkaline region (the N-A isomerization, 1 where N and A indicate the nonaged and aged BMA, respectively) is accelerated in the absence of added salt and suppressed in the presence of salt above 0.10 M. The microenvironment of the SH group was studied using the spinlabel dipstick technique [15,16]. These dipstick results indicated a restrictive environment for the SH group in the N-form and a freer (perhaps a funnel-shaped crevice) environment for the A-form in 0.10 M sodium phosphate buffer, pH 6.4 [16].…”

Thiol dependent isomerization of bovine albumin

“…Thiol disulfide interchange has been proposed as the mechanism underlying albumin isomerization [4,7,8] and can be considered as a multi-step process involving the presence of different species, one of them being reduced cysteine residues. We attempted to trap these intermediates by stopping the reaction with acid at pH 3, which quenches the reactive thiolate anion.…”