Characterization and Functional Investigation of CGFS-Type Glutaredoxins: A Family of Fe-S Cluster Containing Proteins Involved in Fe-S Cluster Biogenesis
University of Georgia
Monday, March 26, 2012 - 11:15am
Chemistry, Room 400
Glutaredoxin proteins with strictly conserved CGFS active site motifs (CGFS Grxs) are specifically required for Fe-S cluster biogenesis as suggested by recent studies of Saccharomyces cerevisiae (Sc) Grx5, a yeast mitochondrial CGFS Grx.1-3Moreover, most CGFS Grxs from other organisms can functionally substitute for Sc Grx5 when targeted to the mitochondrial matrix and their ability to incorporate a labile subunit-bridging [2Fe-2S]2+ clusters utilizing the active-site cysteine residues and two glutathione (GSH) molecules and to transfer preassembled clusters to Fe-S cluster-requiring proteins, suggests putative roles for CGFS Grxs in the assembly, storage or delivery of Fe-S clusters and as sensors of the cellular Fe and/or Fe-S cluster status.4,5However, the precise role(s) of CGFS Grxs remain to be elucidated. This talk will present spectroscopic characterization of the Fe-S cluster-bound forms of ScGrx5, and provide evidence for a dimeric form either containing one linear-type [3Fe-4S]+ cluster in the presence of GSH or containing one cubane-type [4Fe-4S]2+ cluster in the presence of DTT. Our results indicate a role for S. cerevisiaeGrx5 in GSH-dependent scavenging and recycling Fe-S clusters released during protein unfolding and in maturation of [4Fe-4S] cluster-containing proteins in mitochondria. In addition, spectroscopic and functional characterization of the [2Fe-2S]2+ clusters in two Azotobacter vinelandii (Av) CGFS Grxs, AvGrx5 and AvGrx-nif, have provided in vitroevidence for their involvement in Fe-S cluster trafficking. The results show that AvGrx5 and AvGrx-nif are competent to function in [2Fe-2S] cluster storage and trafficking in isc- and nif-specific Fe-S cluster biogenesis systems, respectively.
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