Note: K.B. and S.M.K. contributed equally to this work.
Plasmoredoxin, a novel redox-active protein unique for malarial parasites
Article first published online: 27 FEB 2003
European Journal of Biochemistry
Volume 270, Issue 6, pages 1057–1064, March 2003
How to Cite
Becker, K., Kanzok, S. M., Iozef, R., Fischer, M., Schirmer, R. H. and Rahlfs, S. (2003), Plasmoredoxin, a novel redox-active protein unique for malarial parasites. European Journal of Biochemistry, 270: 1057–1064. doi: 10.1046/j.1432-1033.2003.03495.x
- Issue published online: 27 FEB 2003
- Article first published online: 27 FEB 2003
- (Received 2 December 2002, revised 28 January 2003, accepted 3 February 2003)
- Plasmodium falciparum;
- thioredoxin superfamily
Thioredoxins are a group of small redox-active proteins involved in cellular redox regulatory processes as well as antioxidant defense. Thioredoxin, glutaredoxin, and tryparedoxin are members of the thioredoxin superfamily and share structural and functional characteristics. In the malarial parasite, Plasmodium falciparum, a functional thioredoxin and glutathione system have been demonstrated and are considered to be attractive targets for antimalarial drug development.
Here we describe the identification and characterization of a novel 22 kDa redox-active protein in P. falciparum. As demonstrated by in silico sequence analyses, the protein, named plasmoredoxin (Plrx), is highly conserved but found exclusively in malarial parasites. It is a member of the thioredoxin superfamily but clusters separately from other members in a phylogenetic tree. We amplified the gene from a gametocyte cDNA library and overexpressed it in E. coli. The purified gene product can be reduced by glutathione but much faster by dithiols like thioredoxin, glutaredoxin, trypanothione and tryparedoxin. Reduced Plrx is active in an insulin-reduction assay and reduces glutathione disulfide with a rate constant of 640 m−1·s−1 at pH 6.9 and 25 °C; glutathione-dependent reduction of H2O2 and hydroxyethyl disulfide by Plrx is negligible. Furthermore, plasmoredoxin provides electrons for ribonucleotide reductase, the enzyme catalyzing the first step of DNA synthesis. As demonstrated by Western blotting, the protein is present in blood-stage forms of malarial parasites.
Based on these results, plasmoredoxin offers the opportunity to improve diagnostic tools based on PCR or immunological reactions. It may also represent a specific target for antimalarial drug development and is of phylogenetic interest.