Urbs1 protein, a fungal iron uptake regulator from Ustilago maydis, contains two GATA-1-type zinc finger motifs. The finger motifs of Urbs1 bind to a target DNA sequence in the sid1 gene promoter region when the iron level in the growth medium is high. The effect of this binding is repression of transcription of the sid1 gene, thus preventing the cell from accumulating iron to a toxic level. On the other hand, when iron is limited in the growth media, Urbs1 will not bind to target DNA, thus the cell can transport needed amounts of iron for growth. To investigate how Urbs1 interacts with it's target DNA sequence, the single and double zinc finger motifs of Urbs1 with MW of 8.7, 10 and 23 kD, respectively will be overexpressed in E. coli. Subsequent 13C- and 15N-labeled proteins will be prepared. Multidimensional and multinuclear NMR studies will be performed on the purified proteins to obtain the 3D structures.