title: The multidomain thioredoxin-monothiol glutaredoxins represent a distinct functional group.
abstract: Monothiol glutaredoxins (Grxs) with a noncanonical CGFS active site are found in all kingdoms of life. They include members with a single domain and thioredoxin-Grx fusion proteins. In Saccharomyces cerevisiae, the multidomain Grx3 and Grx4 play an essential role in intracellular iron trafficking. This crucial task is mediated by an essential Fe/S cofactor. This study shows that this unique physiological role cannot be executed by single domain Grxs, because the thioredoxin domain is indispensable for function in vivo. Mutational analysis revealed that a CPxS active site motif is fully compatible with Fe/S cluster binding on Grx4, while a dithiol active site results in cofactor destabilization and a moderate impairment of in vivo function. These requirements for Fe/S cofactor stabilization on Grx4 are virtually the opposite of those previously reported for single domain Grxs. 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 multidomain monothiol Grxs form a unique protein family distinct from that of the single domain Grxs.
authors.affiliation: Institut für Zytobiologie und Zytopathologie, Philipps-Universität Marburg, Germany.
authors.forename: Bastian
authors.initials: B
authors.lastname: Hoffmann
authors.forename: Marta A
authors.initials: MA
authors.lastname: Uzarska
authors.forename: Carsten
authors.initials: C
authors.lastname: Berndt
authors.forename: José R
authors.initials: JR
authors.lastname: Godoy
authors.forename: Petra
authors.initials: P
authors.lastname: Haunhorst
authors.forename: Christopher Horst
authors.initials: CH
authors.lastname: Lillig
authors.forename: Roland
authors.initials: R
authors.lastname: Lill
authors.forename: Ulrich
authors.initials: U
authors.lastname: Mühlenhoff
mesh_terms: D020134:Catalytic Domain; D054477:Glutaredoxins / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism
chemical_list: D054477:Glutaredoxins; C516012:Grx4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D013879:Thioredoxins; C559907:GRX4 protein, S pombe