SEQUENCE-ANALYSIS OF THE TRYPAREDOXIN PEROXIDASE GENE FROM CRITHIDIA-FASCICULATA AND ITS FUNCTIONAL EXPRESSION IN ESCHERICHIA-COLI

Tryparedoxin peroxidase from Crithidia fasciculata is an essential com ponent of the trypanothione-dependent hydroperoxide metabolism in the trypanosomatids (Nogoceke, E., Gommel, D, U,, Kie beta, M,, Kalisz, H. M,, and Flohe, L, (1997) Biol. Chem, 378, 827-836), The tryparedoxin peroxidase gene and its flanking regions have been isolated and sequen ced from a C, fasciculata genomic DNA library, It consists of an open reading frame of 564 base pairs encoding a protein of 188 amino acid r esidues, The gene, modified to encode 6 additional histidine residues, was expressed in Escherichia coli and the recombinant protein was pur ified to homogeneity by metal chelating chromatography, Recombinant tr yparedoxin peroxidase has a subunit molecular mass of 21884 +/- 22 and contains two isoforms of pi 6.2 and 6.3, It exhibits a kinetic patter n identical to that of the authentic tryparedoxin peroxidase and has a similar specific activity of 2.51 units mg-l, The enzyme unequivocall y belongs to the peroxiredoxin family of proteins, whose members have been found in all phyla, A phylo genetic tree comprising 47 protein an d DNA sequences showed tryparedoxin peroxidase and a homologous Trypan osoma blucei sequence to form a distinct molecular clade, The consensu s sequence: -16)Gx(3)Rx(2)Fx(2)Dx(27)Ax(1)Qx(4-11)Cx(1-3)Wx(n) was dem onstrated by alignment of the sequences of tryparedoxin peroxidase and 8 other peroxiredoxins with established peroxidase function.