Structures of tryparedoxins revealing interaction with trypanothione.
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.
Hofmann
B
B
Department of Biochemistry, Technical University of Braunschweig, Germany.
Budde
H
H
Bruns
K
K
Guerrero
S A
SA
Kalisz
H M
HM
Menge
U
U
Montemartini
M
M
Nogoceke
E
E
Steinert
P
P
Wissing
J B
JB
Flohé
L
L
Hecht
H J
HJ
D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D016831:Crithidia fasciculata; D018360:Crystallography, X-Ray / Q000379:methods; D003545:Cysteine; D005978:Glutathione / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D012694:Serine; D013095:Spermidine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D013879:Thioredoxins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
C114110:tryparedoxin; C012333:glutathionylspermidine; D012694:Serine; D013879:Thioredoxins; C044809:trypanothione; D005978:Glutathione; D003545:Cysteine; D013095:Spermidine