CutA are a protein family present in bacteria, plants, and animals, including humans. Escherichia coli CutA is involved in copper tolerance, whereas mammalian proteins are implicated in the anchoring of acetylcholinesterase in neuronal cell membranes. Here we report crystal structure of the divalent-cation tolerance protein CutA from Yersinia pestis. Biological assembly is a homo trimer. Each subunit consists of a ferredoxin-like (beta1alpha1beta2beta3alpha2beta4) fold with an additional strand (beta5), a C-terminal helix (alpha3), and an unusual extended beta-hairpin involving strands beta2 and beta3. The evolutionarily conserved trimeric assembly of CutA is reminiscent of the architecture of PII signal transduction proteins. This similarity suggests an intriguing role of CutA proteins in signal transduction through allosteric communications between subunits.