Verification of the Interaction of a Tryparedoxin Peroxidase with Tryparedoxin by ESI-MS/MS
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H. Budde
Abstract
Tryparedoxin peroxidases (TXNPx) catalyze hydroperoxide reduction by tryparedoxin (TXN) by an enzyme substitution mechanism presumed to involve three catalytic intermediates: (i) a transient oxidation state having C52 oxidized to a sulfenic acid, (ii) the stable oxidized form with C52 disulfide-bound to C173', and (iii) a semi-reduced intermediate with C40 of TXN disulfide-linked to C173' from which the ground state enzyme is regenerated by thiol/disulfide reshuffling. This kinetically unstable form was mimmicked by a dead-end intermediate generated by cooxidation of TXNPx of Trypanosoma brucei brucei with an inhibitory mutein of TXN in which C43 was replaced by serine (TbTXNC43S). Cleavage of the isolated dead-end intermediate by trypsin plus chymotrypsin yielded a fragment that complied in size with the TbTXNC43S sequence 36 to 44 disulfide-linked to the TbTXNPx sequence 169 to 177. The presumed nature of the proteolytic fragment was confirmed by MS/MS sequencing. The results provide direct chemical evidence for the assumption that the reductive part of the catalysis is initiated by an attack of the substrates solvent-exposed C40 on C173 of the oxidized peroxidase and, thus, confirm the hypothesis on the interaction of 2-Cys-peroxiredoxins with their proteinaceous substrates.
Copyright © 2003 by Walter de Gruyter GmbH & Co. KG
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Articles in the same Issue
- Paper of the Year 2002
- Terminal Differentiation of Epithelia
- Use of Detergents to Study Membrane Rafts: The Good, the Bad, and the Ugly
- Protein Structure Similarity as Guiding Principle for Combinatorial Library Design
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- Function and Structure of N-Terminal and C-Terminal Domains of Calcineurin B Subunit
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