Structural basis for the different activities of yeast Grx1 and Grx2.
ABSTRACT Yeast glutaredoxins Grx1 and Grx2 catalyze the reduction of both inter- and intra-molecular disulfide bonds using glutathione (GSH) as the electron donor. Although sharing the same dithiolic CPYC active site and a sequence identity of 64%, they have been proved to play different roles during oxidative stress and to possess different glutathione-disulfide reductase activities. To address the structural basis of these differences, we solved the crystal structures of Grx2 in oxidized and reduced forms, at 2.10 A and 1.50 A, respectively. With the Grx1 structures we previously reported, comparative structural analyses revealed that Grx1 and Grx2 share a similar GSH binding site, except for a single residue substitution from Asp89 in Grx1 to Ser123 in Grx2. Site-directed mutagenesis in combination with activity assays further proved this single residue variation is critical for the different activities of yeast Grx1 and Grx2.
- SourceAvailable from: gbv.de07/2009; 58(4):725-725.
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ABSTRACT: Glutaredoxins act as reducing agents for the large subunit of ribonucleotide reductase (R1) in many prokaryotes and eukaryotes, including humans. The same relationship has been proposed for the glutaredoxin and R1 proteins expressed by all orthopoxviruses, including vaccinia, variola, and ectromelia virus. Interestingly, the orthopoxviral proteins share 45% and 78% sequence identity with human glutaredoxin-1 (Grx-1) and R1, respectively. To study structure-function relationships of the vertebrate Grx-1 family, and reveal potential viral adaptations, we have determined crystal structures of the ectromelia virus glutaredoxin, EVM053, in the oxidized and reduced states. The structures show a large redox-induced conformational rearrangement of Tyr21 and Thr22 near the active site. We predict that the movement of Tyr21 is a viral-specific adaptation that increases the redox potential by stabilizing the reduced state. The conformational switch of Thr22 appears to be shared by vertebrate Grx-1 and may affect the strictly conserved Lys20. A crystal packing-induced structural change in residues 68-70 affects the GSH-binding loop, and our structures reveal a potential interaction network that connects the GSH-binding loop and the active site. EVM053 also exhibits a novel cis-proline (Pro53) in a loop that has been shown to contribute to R1-binding in Escherichia coli Grx-1. The cis-peptide bond of Pro53 may be required to promote electrostatic interactions between Lys52 and the C-terminal carboxylate of R1. Finally, dimethylarsenite was covalently attached to Cys23 in one reduced EVM053 structure and our preliminary data show that EVM053 has dimethylarsenate reductase activity.Journal of Molecular Biology 03/2007; 365(5):1545-58. · 3.91 Impact Factor
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ABSTRACT: Iron-sulfur (Fe/S) clusters require a complex set of proteins to become assembled and incorporated into apoproteins in a living cell. Researchers have described three distinct assembly systems in eukaryotes that are involved in the maturation of cellular Fe/S proteins. Mitochondria are central for biogenesis. They contain the ISC-the iron-sulfur cluster assembly machinery that was inherited from a similar system of eubacteria in evolution and is involved in biogenesis of all cellular Fe/S proteins. The basic principle of mitochondrial (and bacterial) Fe/S protein maturation is the synthesis of the Fe/S cluster on a scaffold protein before the cluster is transferred to apoproteins. Biogenesis of cytosolic and nuclear Fe/S proteins is facilitated by the cytosolic iron-sulfur protein assembly (CIA) apparatus. This process requires the participation of mitochondria that export a still unknown component via the ISC export machinery, including an ABC transporter.Annual Review of Cell and Developmental Biology 02/2006; 22:457-86. · 17.98 Impact Factor