Streptomyces coelicolor SC04226 is a nickel binding protein

Abstract

The open reading frame SC04226 of Streptomyces coelicolor A3(2) encodes an 82-residue hypothetical protein. Biochemical assays revealed that each SC04226 dimer binds four nickel ions. To decipher the molecular function, we solved the crystal structures of SC04226 in both apo- and nickel-bound (Ni-SC04226) forms at 1.30 and 2.04 Ä resolution, respectively. Each subunit of SC04226 dimer adopts a canonical ferredoxin-like fold with five ß-strands flanked by two α-helices. in the structure of Ni-SC04226, four nickel ions are coordinated at the surface of the dimer. Further biochemical assays suggested that the binding of Ni2+ triggers the self-aggregation of SC04226 in vitro. In addition, RT-qPCR assays demonstrated that the expression of SC04226 gene in S. coelicolor is specifically up-regulated by the addition of Ni2+ , but not other divalent ions such as Cu2+, Mn2+ or Co2+ . All these results suggested that SC04226 acts as a nickel binding protein, probably required for nickel sequestration and/or detoxification.