Redox properties of a thioredoxin-like Arabidopsis protein, AtTDX

Sang Kim, Y. H. Chi, Jeffrey Lee, S. R. Schlesinger, Masoud Zabet Moghaddam, J. S. Chung, David Knaff, Sang Kim, Sang Kim

Research output: Contribution to journalArticle

Abstract

AtTDX is an enzyme present in Arabidopsis thaliana which is composed of two domains, a thioredoxin (Trx)-motif containing domain and a tetratricopeptide (TPR)-repeat domain. This enzyme has been shown to function as both a thioredoxin and a chaperone. The midpoint potential (E(m)) of AtTDX was determined by redox titrations using the thiol-specific modifiers, monobromobimane (mBBr) and mal-PEG. A NADPH/Trx reductase (NTR) system was used both to validate these E(m) determination methods and to demonstrate that AtTDX is an electron-accepting substrate for NTR. Titrations of full-length AtTDX revealed the presence of a single two-electron couple with an E(m) value of approximately -260 mV at pH 7.0. The two cysteines present in a typical, conserved Trx active site (WCGPC), which are likely to play a role in the electron transfer processes catalyzed by AtTDX, have been replaced by serines by site-directed mutagenesis. These replacements (i.e., C304S, C307S, and C304S/C307S) resulted in a
Original languageEnglish
Pages (from-to)2213–2221
JournalBiochim. Biophys. Acta
StatePublished - Dec 2010

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