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Títol:
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Biochemical characterization of yeast mitochondrial Grx5 monothiol glutaredoxin
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Autor/a:
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Tamarit Sumalla, Jordi; Bellí i Martínez, Gemma; Cabiscol Català, Elisa; Herrero Perpiñán, Enrique; Ros Salvador, Joaquim
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Notes:
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Grx5 is a yeast mitochondrial protein involved in iron-
sulfur biogenesis that belongs to a recently described
family of monothiolic glutaredoxin-like proteins. No
member of this family has been biochemically charac-
terized previously. Grx5 contains a conserved cysteine
residue (Cys-60) and a non-conserved one (Cys-117). In
this work, we have purified wild type and mutant C60S
and C117S proteins and characterized their biochemical
properties. A redox potential of ؊175 mV was calculated
for wild type Grx5. The pKa values obtained by titration
of mutant proteins with iodoacetamide at different pHs
were 5.0 for Cys-60 and 8.2 for Cys-117. When Grx5 was
incubated with glutathione disulfide, a transient mixed
disulfide was formed between glutathione and the cys-
tein 60 of the protein because of its low pKa. Binding of
glutathione to Cys-60 promoted a decrease in the Cys-
117 pKa value that triggered the formation of a disulfide
bond between both cysteine residues of the protein, in-
dicating that Cys-117 plays an essential role in the cat-
alytic mechanism of Grx5. The disulfide bond in Grx5
could be reduced by GSH but at a rate at least 20 times
slower than that observed for the reduction of glutare-
doxin 1 from E. coli, a dithiolic glutaredoxin. This slow
reduction rate could suggest that GSH may not be the
physiologic reducing agent of Grx5. The fact that wild
type Grx5 efficiently reduced a glutathiolated protein
used as a substrate indicated that Grx5 may act as a
thiol reductase inside the mitochondria. |
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Drets:
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(c) The American Society for Biochemistry and Molecular Biology, 2003
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Tipus de document:
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article
publishedVersion |
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Publicat per:
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The American Society for Biochemistry and Molecular Biology
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