The reactions of inter- and intra-chain disulphide bonds in proteins with sulphite

Abstract

The reaction is strictly reversible and will go to completion only under conditions where the concentration of RS-is small, as for instance at pH 7 (Stricks & Kolthoff, 1951; Cecil & McPhee, 1955). Insulin has two disulphide bonds linking the A and B chains and a third intra-chain bond linking residues 6 and 11 (referred to below as the 6-11 intra-chain bond) on the A chain (Ryle, Sanger, Smith & Kitai, 1955). Cecil & Loening (1960) studied the reaction of these disulphide bonds with sulphite. They found that 'the two inter-chain bonds react with sulphite at pH 7 causing the insulin to split into its component A and B chains. The 6-11 intra-chain bond does not react with sulphite alone but it will react with sulphite in the presence of phenylmercuric hydroxide. Partial reaction occurs in the presence of urea or guanidine. The explanation suggested by Cecil & Loening for this difference in the reactivity of the inter-and intra-chain disulphide bonds was that the structure of the 6-11 intra-chain ring is stabilized by hydrogen bonds (or other non-covalent bonds) rather than by the disulphide bond. This would have the effect of shifting the equilibrium of the reaction with sulphite to the left since the ring would have no tendency to open when the disulphide bond is split. Phenylmercuric hydroxide would block the reverse reaction by combining with the thiol formed. Urea and guanidine would reduce the stability of the 6-11 intra-chain ring by breaking the non-covalent bonds. In these cases the disulphide bond would be expected to react. Bovine serum albumin has 17 disulphide bonds and these appear to behave similarly to the 6-11 intra-chain bond in insulin. Kolthoff, Anastasi & Tan (1958, 1959) found that there was no appreciable reaction with sulphite alone but that all 17 bonds reacted with sulphite in the presence of mercuric chloride. In the presence of guanidine 12-13 bonds reacted with sulphite. Hunter & McDuffie (1959) have shown that the molecular

The Role of the Reactive Disulfide Bond in the Interaction of Cholera‐Toxin Functional Regions

“…This difference in the susceptibility of the inter-chain and intra-chain disulfide bonds to reduction has been explained by Cecil and Wake [34]. They proposed that intra-chain disulfide bonds commonly form compact ring structures stabilized by hydrogen bonds (or other non-covalent bonds).…”

Facile sulfitolysis of the disulfide bonds in oxidized thioredoxin and glutaredoxin

“…Another case of facilitated sulfitolysis with physiological significance, produced by 1 mM sulfite, concerns the mixed-disulfide bond present in the non-mercaptalbumin fraction of rabbit plasma proteins [12]. In contrast, insulin undergoes partial sulfitolysis only in 20-3OmM sulfite solution and the internal disulfide bridges in larger proteins such as lysozyme, ribonuclease, or bovine serum albumin are largely resistant to sulfite in the absence of denaturants [6], excluding a role as toxicological targets.…”

PHOTOSYNTHETIC 14C FIXATION BY THE LICHEN UMBILICARIA MUHLENBERGH (ACH) TUCK. FOLLOWING SHORT EXPOSURES TO AQUEOUS SULPHUR DIOXIDE

“…RuDP carboxylase (Ziegler, 1972). Finally, the ability of bisulphite to cleave disulphide bonds in proteins is a potential mode of attack (Mahler and Cordes, 1966, p. 74;Roy and Trudinger, 1970 p. 16;Bailey and Cole, 1959;Cecil and Wake, 1962). This cleavage causes changes in the tertiary structure of proteins leading to deactivation in the case of enzymes.…”