Structures of tryparedoxins revealing interaction with trypanothione

• Published in: Biological chemistry Vol. 382; no. 3; p. 459
• Main Authors: Hofmann, B, Budde, H, Bruns, K, Guerrero, S A, Kalisz, H M, Menge, U, Montemartini, M, Nogoceke, E, Steinert, P, Wissing, J B, Flohé, L, Hecht, H J
• Format: Journal Article
• Language: English
• Published: Germany 01-03-2001
• Subjects: Amino Acid Sequence; Animals; Catalytic Domain; Crithidia fasciculata; Crystallography, X-Ray - methods; Cysteine; Glutathione - analogs & derivatives; Glutathione - chemistry; Glutathione - metabolism; Models, Molecular; Molecular Sequence Data; Mutagenesis, Site-Directed; Protein Conformation; Sequence Homology, Amino Acid; Serine; Spermidine - analogs & derivatives; Spermidine - chemistry; Spermidine - metabolism; Thioredoxins - chemistry; Thioredoxins - genetics; Thioredoxins - metabolism
• ISSN: 1431-6730
• DOI: 10.1515/BC.2001.056

Tryparedoxins (TXNs) catalyse the reduction of peroxiredoxin-type peroxidases by the bis-glutathionyl derivative of spermidine, trypanothione, and are relevant to hydroperoxide detoxification and virulence of trypanosomes. The 3D-structures of the following tryparedoxins are presented: authentic tryparedoxin1 of Crithidia fasciculata, CfTXN1; the his-tagged recombinant protein, CfTXN1H6; reduced and oxidised CfTXN2, and an alternative substrate derivative of the mutein CfTXN2H6-Cys44Ser. Cys41 (Cys40 in TXN1) of the active site motif 40-WCPPCR-45 proved to be the only solvent-exposed redox active residue in CfTXN2. In reduced TXNs, its nucleophilicity is increased by a network of hydrogen bonds. In oxidised TXNs it can be attacked by the thiol of the 1N-glutathionyl residue of trypanothione, as evidenced by the structure of 1N-glutathionylspermidine-derivatised CfTXN2H6-Cys44Ser. Modelling suggests Arg45 (44), Glu73 (72), the Ile110 (109) cis-Pro111 (110)-bond and Arg129 (128) to be involved in the binding of trypanothione to CfTXN2 (CfTXN1). The model of TXN-substrate interaction is consistent with functional characteristics of known and newly designed muteins (CfTXN2H6-Arg129Asp and Glu73Arg) and the 1N-glutathionyl-spermidine binding in the CfTXN2H6-Cys44Ser structure.