title: Plasmodium falciparum possesses a classical glutaredoxin and a second, glutaredoxin-like protein with a PICOT homology domain.
abstract: The genes coding for two different proteins with homologies to glutaredoxins have been identified in the genome of the malarial parasite Plasmodium falciparum. Both genes were amplified from a gametocytic cDNA and overexpressed in Escherichia coli. The smaller protein (named PfGrx-1) with 12.4 kDa in size exhibits the typical glutaredoxin active site motif "CPYC," shows glutathione-dependent glutaredoxin activity in the beta-hydroxyethyl disulfide (HEDS) assay, and reduces Trypanosoma brucei ribonucleotide reductase. Glutathione:HEDS transhydrogenase activity (approximately 60 milliunits/mg of protein) was clearly detectable in trophozoite extracts from eight different P. falciparum strains and did not differ between chloroquine-resistant and -sensitive parasites. Five different antimalarial drugs at 100 microm did not significantly influence isolated PfGrx-1 activity. In contrast, the second protein (deduced mass 19.9 kDa) with homology to glutaredoxins (31% identity to Schizosaccharomyces pombe in a 140-amino acid overlap) was not active in the HEDS assay; however, its general dithiol reducing activity was demonstrated in the insulin assay in the presence of dithiothreitol. Interestingly, the sequence contains a PICOT (for protein kinase C-interacting cousin of thioredoxin) homology domain, which might suggest regulatory functions of the protein. We named this protein PfGLP-1, for P. falciparum 1-Cys-glutaredoxin-like protein-1. In contrast to glutaredoxins, PfGLP-1 could not be reduced by glutathione. This is the first report on glutaredoxin-like proteins in the family of Plasmodia.
authors.affiliation: Interdisciplinary Research Center, Justus Liebig University, 35392 Giessen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Rahlfs
authors.forename: M
authors.initials: M
authors.lastname: Fischer
authors.forename: K
authors.initials: K
authors.lastname: Becker
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry; D003001:Cloning, Molecular; D016054:DNA, Protozoan / Q000032:analysis; D054477:Glutaredoxins; D007328:Insulin / Q000378:metabolism; D008969:Molecular Sequence Data; D010088:Oxidoreductases; D010963:Plasmodium falciparum / Q000737:chemistry / Q000235:genetics*; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D012264:Ribonucleotide Reductases / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D002352:Carrier Proteins; D016054:DNA, Protozoan; D054477:Glutaredoxins; C438386:Grx-1 protein, Plasmodium falciparum; D007328:Insulin; D011506:Proteins; D015800:Protozoan Proteins; D011994:Recombinant Proteins; D010088:Oxidoreductases; D012264:Ribonucleotide Reductases