Novel Glutaredoxin Activity of the Yeast Prion Protein Ure2 Reveals a Native-like Dimer within Fibrils*

AUTOR(ES)

Zhang, Zai-Rong

FONTE

American Society for Biochemistry and Molecular Biology

RESUMO

Ure2 is the protein determinant of the Saccharomyces cerevisiae prion [URE3]. Ure2 has structural similarity to glutathione transferases, protects cells against heavy metal and oxidant toxicity in vivo, and shows glutathione-dependent peroxidase activity in vitro. Here we report that Ure2 (which has no cysteine residues) also shows thiol-disulfide oxidoreductase activity similar to that of glutaredoxin enzymes. This demonstrates that disulfide reductase activity can be independent of the classical glutaredoxin CXXC/CXXS motif or indeed an intrinsic catalytic cysteine residue. The kinetics of the glutaredoxin activity of Ure2 showed positive cooperativity for the substrate glutathione in both the soluble native state and in amyloid-like fibrils, indicating native-like dimeric structure within Ure2 fibrils. Characterization of the glutaredoxin activity of Ure2 sheds light on its ability to protect yeast from heavy metal ion and oxidant toxicity and suggests a role in reversible protein glutathionylation signal transduction. Observation of allosteric enzyme behavior within amyloid-like Ure2 fibrils not only provides insight into the molecular structure of the fibrils but also has implications for the mechanism of [URE3] prion formation.

Documentos Relacionados

• Native-like structure of a protein-folding intermediate bound to the chaperonin GroEL
• Improved recognition of native-like protein structures using a family of designed sequences
• The yeast prion [URE3] can be greatly induced by a functional mutated URE2 allele
• The yeast prion Ure2p retains its native α-helical conformation upon assembly into protein fibrils in vitro
• Specificity of native-like interhelical hydrophobic contacts in the apomyoglobin intermediate