Mechanistic Details of Glutathione Biosynthesis Revealed by Crystal Structures of Saccharomyces cerevisiae Glutamate Cysteine Ligase*
AUTOR(ES)
Biterova, Ekaterina I.
FONTE
American Society for Biochemistry and Molecular Biology
RESUMO
Glutathione is a thiol-disulfide exchange peptide critical for buffering oxidative or chemical stress, and an essential cofactor in several biosynthesis and detoxification pathways. The rate-limiting step in its de novo biosynthesis is catalyzed by glutamate cysteine ligase, a broadly expressed enzyme for which limited structural information is available in higher eukaryotic species. Structural data are critical to the understanding of clinical glutathione deficiency, as well as rational design of enzyme modulators that could impact human disease progression. Here, we have determined the structures of Saccharomyces cerevisiae glutamate cysteine ligase (ScGCL) in the presence of glutamate and MgCl2 (2.1 Å; R = 18.2%, Rfree = 21.9%), and in complex with glutamate, MgCl2, and ADP (2.7 Å; R = 19.0%, Rfree = 24.2%). Inspection of these structures reveals an unusual binding pocket for the α-carboxylate of the glutamate substrate and an ATP-independent Mg2+ coordination site, clarifying the Mg2+ dependence of the enzymatic reaction. The ScGCL structures were further used to generate a credible homology model of the catalytic subunit of human glutamate cysteine ligase (hGCLC). Examination of the hGCLC model suggests that post-translational modifications of cysteine residues may be involved in the regulation of enzymatic activity, and elucidates the molecular basis of glutathione deficiency associated with patient hGCLC mutations.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2781686Documentos Relacionados
- Cysteine biosynthesis in Saccharomyces cerevisiae: mutation that confers cystathionine beta-synthase deficiency.
- The iodide-catalyzed decomposition of hydrogen peroxide: mechanistic details of an old reaction as revealed by electrospray ionization mass spectrometry monitoring
- Crystal Structures of a Poplar Xyloglucan Endotransglycosylase Reveal Details of Transglycosylation Acceptor Binding
- GDH3 encodes a glutamate dehydrogenase isozyme, a previously unrecognized route for glutamate biosynthesis in Saccharomyces cerevisiae.
- Cysteine biosynthesis in Saccharomyces cerevisiae occurs through the transsulfuration pathway which has been built up by enzyme recruitment.