The extreme hyper‐reactivity of selected cysteines drives hierarchical disulfide bond formation in serum albumin. (26th October 2016)

• Record Type: Journal Article
• Authors: Bocedi, Alessio; Fabrini, Raffaele; Pedersen, Jens Z.; Federici, Giorgio; Iavarone, Federica; Martelli, Claudia; Castagnola, Massimo; Ricci, Giorgio
• Is Part Of: FEBS journal. Volume 283:Number 22(2016)
• Page Start: 4113
• Page End: 4127
• Publication Date: 2016-10-26
• Subjects: disulfide -- hyper‐reactivity of cysteines -- oxidative folding -- protein structure -- Serum albumin; Biochemistry -- Periodicals; Molecular biology -- Periodicals; Pathology, Molecular -- Periodicals; 572
• DOI: 10.1111/febs.13909
• Languages: English
• ISSNs: 1742-464X

Abstract

Abstract : After mild reduction of serum albumin, seven among the 34 cysteines forming the disulfide network displayed a surprising hyper‐reactivity. Compared to the thiol group of glutathione, the average reactivity of these cysteines towards disulfides and thiol reagents was more than 100 times higher. Using mass spectrometry and kinetic data, we identified all these unusual residues, with Cys75, Cys123 and Cys264 showing the highest reactivity. This effect was mainly due to a low p K a of the sulfhydryl groups and may explain the very fast formation of early disulfides in the nascent protein suggesting the existence of a hierarchical propensity to form such covalent links in selected regions during oxidative folding. An identical pattern of hyper‐reactive cysteines was found in albumins from six different mammals. This hyper‐reactivity is much higher than the one found in other proteins containing multiple cysteines only devoted to structural disulfide bonds. It is possible that such hyper‐reactive cysteines could also be present in other proteins, although their existence has been completely ignored so far. Abstract : The structure of serum albumin contains an extraordinary complex system of disulfide bridges involving 34 cysteines. New studies on the oxidative folding process show that seven of these cysteines are highly reactive and may form disulfides more than 200 times faster than the other cysteines. This behavior may ensure the correct three‐dimensional folding of the nascent protein.