The crystal structure of human GLRX5: iron-sulfur cluster co-ordination, tetrameric assembly and monomer activity

Journal article

Human GLRX5 (glutaredoxin 5) is an evolutionarily conserved thiol-disulfide oxidoreductase that has a direct role in the maintenance of normal cytosolic and mitochondrial iron homoeostasis, and its expression affects haem biosynthesis and erythropoiesis. We have crystallized the human GLRX5 bound to two [2Fe-2S] clusters and four GSH molecules. The crystal structure revealed a tetrameric organization with the [2Fe-2S] clusters buried in the interior and shielded from the solvent by the conserved β1-α2 loop, Phe⁶⁹ and the GSH molecules. Each [2Fe-2S] cluster is ligated by the N-terminal activesite cysteine (Cys⁶⁷) thiols contributed by two protomers and two cysteine thiols from two GSH. The two subunits co-ordinating the cluster are in a more extended conformation compared with iron-sulfur-bound human GLRX2, and the intersubunit interactions are more extensive and involve conserved residues among monothiol GLRXs. Gel-filtration chromatography and analytical ultracentrifugation support a tetrameric organization of holo-GLRX5, whereas the apoprotein is monomeric. MS analyses revealed glutathionylation of the cysteine residues in the absence of the [2Fe-2S] cluster, which would protect them from further oxidation and possibly facilitate cluster transfer/acceptance. Apo-GLRX5 reduced glutathione mixed disulfides with a rate 100 times lower than did GLRX2 and was active as a glutathione-dependent electron donor for mammalian ribonucleotide reductase.

Authors: Johansson, C; Roos, A; Montano, S; Sengupta, R; Filippakopoulos, P

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Portland Press
• Journal: Biochemical Journal
• Volume: 433
• Issue: 2
• Pages: 303-311
• Publication date: 2010-01-01
• DOI: 10.1042/BJ20101286
• EISSN: 1470-8728
• ISSN: 0264-6021
• Language: English
• Subjects: Crystallography, X-Ray; Protein Binding; Glutaredoxins; Protein Multimerization; Protein Structure, Quaternary; chemistry; Humans; Oxidation-Reduction; Disulfides; Iron-Sulfur Proteins; metabolism; Models, Molecular