RyhB is a sRNA in Escherichia coli that is expressed under iron-limiting conditions and regulates the iron sparing response. The majority of RyhB targets have not been characterized and the role of RNA structure in the sRNA-mRNA interactions is unknown. It is hypothesized that the target mRNA secondary structure influences the ability of RhyB to interact and that the interaction may induce a structural rearrangement that alters gene expression.