Trypanosoma brucei tryparedoxin, a thioredoxin‐like protein in African trypanosomes

Abstract

A gene has been cloned from Trypanosoma brucei which encodes a protein of 144 amino acid residues containing the thioredoxin-like motif WCPPCR. Overexpression of the gene in E. coli resulted in 4 mg pure protein from 100 ml bacterial cell culture. Recombinant T. brucei tryparedoxin acts as a thiol-disulfide oxidoreductase. It is spontaneously reduced by trypanothione. This dithiol, exclusively found in parasitic protozoa, also reduces E. coli glutaredoxin but not thioredoxin. The trypanothione/tryparedoxin couple is an effective reductant of T. brucei ribonucleotide reductase. Like thioredoxins it has a poor GSH:disulfide transhydrogenase activity. The catalytic properties of tryparedoxin are intermediate between those of classical thioredoxins and glutaredoxins which indicates that these parasite proteins may form a new class of thiol-disulfide oxidoreductases.z 1998 Federation of European Biochemical Societies.

The Dithiol Glutaredoxins of African Trypanosomes Have Distinct Roles and Are Closely Linked to the Unique Trypanothione Metabolism

“…T(SH) 2 (27), T. brucei Tpx (19), T. cruzi TR (28), T. brucei glutathione peroxidase type tryparedoxin peroxidase (Px III) (29), T. brucei His 6 -peroxiredoxin type tryparedoxin peroxidase (TXNPx) (30), the small subunit of T. brucei RR (R2) (31), and His-tagged E. coli cysteine desulfurase (9) were prepared as described. The gene for the large subunit (R1) of RR was cloned in the modified pET vector described below, and the tag-free protein was purified by chromatography on two consecutive nickel-NT-Sepharose columns as outlined below for Grx1 and Grx2.…”

Trypanosoma brucei and Trypanosoma cruzi Tryparedoxin Peroxidases Catalytically Detoxify Peroxynitrite via Oxidation of Fast Reacting Thiols

“…(40), was expressed as an N-terminally His-tagged protein that was purified as described previously (32). Molecular mutants of TbTXN were obtained according to Ref.…”

Sequence, heterologous expression and functional characterization of tryparedoxin1 from Crithidia fasciculata

“…The discovery of TXN1 in C. fasciculata as a trypanothione/ peroxiredoxin oxidoreductase and its partial sequencing [7] initially led to the identification of a novel tryparedoxin (TXN2) in the same species [10] and cloning of a TXN in T. brucei [9].…”

“…All three TXNs have been shown to be specifically reduced by trypanothione with comparably low K m values. TXN1 and TXN2 can substitute for each other in the reduction of tryparedoxin peroxidase [11], whereas the TXN of T. brucei was reported to act as a reducing substrate for the ribonucleotide reductase [9]. It appears conceivable that the diversification of the TXNs provides the basis for functional specialization allowing specific reduction of distinct disulfides at the expense of trypanothione.…”

“…The parasitic peroxide metabolism, however, is unlikely to be the only vital function of the trypanothione/tryparedoxin system. Recently, a tryparedoxin has been reported to be a substrate of the ribonucleotide reductase in Trypanosoma brucei thereby being essential for the DNA biosynthesis of the parasite [9].…”