The role of the C‐terminus for catalysis of the large thioredoxin reductase from Plasmodium falciparum

FEBS Letters

Bergmann, Bärbel¹  Gilberger, Tim-Wolf¹  Müller, Sylke¹  Walter, Rolf D¹ 

[1] Biochemical Parasitology, Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Str. 74, D-20359 Hamburg, Germany

关键词: Large thioredoxin reductase;    C-terminal residue;    Site-directed mutagenesis;    Plasmodium falciparum;    DTNB;    5;    5′-dithiobis (2-nitrobenzoate);    TrxR;    thioredoxin reductase;    PfTrxR;    Plasmodium falciparum TrxR;    PfTrxRC535A;    PfTrxR containing alanine at position 535 instead of cysteine;    PfTrxRC540A;    PfTrxR containing alanine at position 540 instead of cysteine;    PfTrxRC535AC540A;    PfTrxR containing alanines at positions 535 and 540 instead of cysteines;    PfTrxRΔ9;    PfTrxR without the last nine C-terminal amino acids;   

DOI  :  10.1016/S0014-5793(98)00270-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The thioredoxin system is one of the major thiol reducing systems of the cell. Recent studies have revealed that Plasmodium falciparum and human thioredoxin reductase represent a novel class of enzymes, which are substantially different from the isofunctional prokaryotic Escherichia coli enzyme. We identified the cysteines Cys⁸⁸ and Cys⁹³ as the redox active disulfide and His⁵⁰⁹ as the active site base [Gilberger, T.-W., Walter, R.D. and Müller, S., J. Biol. Chem. 272 (1997) 29584–29589]. In addition to the active site thiols Cys⁸⁸ and Cys⁹³ the P. falciparum enzyme has another pair of cysteines at the C-terminus: Cys⁵³⁵ and Cys⁵⁴⁰. To assess the possible role of these peripheral cysteines in the catalytic process the single mutants PfTrxRC535A and PfTrxRC540A, the double mutant PfTrxRC535AC540A and the deletion mutant PfTrxRΔ9 (C-terminal deletion of the last nine amino acids) were constructed. All mutants are defective in their thioredoxin reduction activity, although they still show reactivity with 5,5′-dithiobis (2-nitrobenzoate). These data imply that the C-terminal cysteines are crucially involved in substrate coordination and/or electron transfer during reduction of the peptide substrate.

【 授权许可】

Unknown