Toward a refined classification of class I dithiol glutaredoxins from poplar: biochemical basis for the definition of two subclasses

摘要: Glutaredoxins (Grxs) are small oxidoreductases particularly specialized in the reduction of protein-glutathione adducts. Compared to other eukaryotic organisms, higher plants present an increased diversity Grxs which organized into four classes. This work presents a thorough comparative analysis biochemical and catalytic properties dithiol class I from poplar, namely GrxC1, GrxC2, GrxC3 GrxC4. By evaluating vitro oxidoreductase activity wild type cysteine mutated variants by determining their dithiol-disulfide redox potentials, pKa values cysteine, state changes response oxidative treatments, two subgroups can be distinguished. In accordance with probable quite recent duplication, GrxC1 GrxC2 less efficient catalysts for dehydroascorbate hydroxyethyldisulfide compared GrxC4, they form covalent dimers owing presence additional C-terminal (CysC). Interestingly, second active site (CysB) influences reactivity (CysA) as already observed GrxC5 (restricted A. thaliana), but not C4. However, all proteins intramolecular disulfide between cysteines (CysA-CysB) could represent either protective mechanism considering that this is dispensable deglutathionylation reaction or true intermediate occurring during particular substrates specific conditions compartments where glutathione levels insufficient support Grx regeneration. Overall, addition different sub-cellular localization expression pattern, duplication maintenance along evolution several explained existence differential properties.