Hoffmann B, Uzarska MA, Berndt C, Godoy JR, Haunhorst P, Lill R, Lillig CH, Muhlenhoff U

Monothiol glutaredoxins with a non-canonical CGFS active site are found in all kingdoms of life. They include members with a single domain and thioredoxin-glutaredoxin fusion proteins. In S. cerevisiae, the multi-domain Grx3 and Grx4 play an essential role in intracellular iron trafficking. This crucial task is mediated by an essential ...

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Fe/S co-factor. Here we show that this unique physiological role cannot be executed by single domain glutaredoxins, because the thioredoxin domain is indispensable for function in vivo. Mutational analysis revealed that a CPxS active site motive is fully compatible with Fe/S cluster binding on Grx4, while a dithiol active site results in co-factor destabilization and a moderate impairment of in vivo function. These requirements for Fe/S co-factor stabilization on Grx4 are virtually the opposite of those previously reported for single domain glutaredoxins. Grx4 functions as iron sensor for the iron-sensing transcription factor Aft1 in S. cerevisiae. We found that Aft1 binds to a conserved binding site at the C-terminus of Grx4. This interaction is essential for the regulation of Aft1. Collectively, our analysis demonstrates that the multi-domain monothiol Grx form a unique protein family distinct from that of the single domain glutaredoxins.

Date: Feb. 08, 2011

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