Download citation
Acta Cryst. (2014). A70, C1406
Download citation
link to html
The ubiquitous iron-sulfur (Fe-S) cluster-containing proteins are involved in countless biological routes and play crucial roles for the functioning of both prokaryotic and eukaryotic cells. The transcription factor IscR, of the helix-turn-helix family, was first implicated in repressing expression of the ISC (Iron Sulfur Cluster biogenesis) pathway and was shown to contain a [2Fe-2S] cluster. Promoters controlled by IscR belong to two distinct sequence groups [1] and the [2Fe-2S] cluster of IscR was shown to be essential for regulation of type-1 promoters (isc, yadR, yhgI), while apo-IscR is responsible for the regulation of type-2 promoters [2]. The proposed model for IscR action consists on a mechanism for Fe-S biogenesis fine-tuned by the cellular Fe-S cluster status. Despite recent advances in understanding the regulation of isc and suf operons by environmental signals, the features of IscR target-site recognition and the structural changes that alter the DNA binding specificity of IscR upon ligation of the [2Fe-2S] cluster are unknown. To understand how IscR recognizes two different DNA motifs, we solved the three-dimensional structures of free apo-IscR and of its complex with a type-2 target sequence, the hya promoter from the hydrogenase-1 operon [3]. These experimental models revealed some of the molecular details of the unusual environmentally modulated recognition of two distinct promoter consensus sequences by IscR, using a single predicted helix-turn-helix DNA binding motif. To our knowledge, IscR is the only transcription factor that is active in both the apo and holo-forms and which displays cofactor-mediated modulation of its DNA binding specificity. This work was funded by Fundação para a Ciência e a Tecnologia (Portugal) through grant PTDC/BBB-BEP/2127/2012 (EU-FEDER funding through COMPETE FCOMP-01-0124-FEDER-028116) and PhD fellowship SFRH/BD/66461/2009 to JAS.

Follow Acta Cryst. A
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds