Issue Date: June 9, 2008
Three Protein Copper Sites Interconnected
The copper sites in cupredoxins, a family of proteins that facilitate a variety of redox activities, are structurally and functionally diverse. As little as 10% of their amino acid sequence is identical. Nevertheless, the copper sites are always found within a similar β-barrel protein structure and may be evolutionarily linked. Studies on the binuclear CuA (purple) site of nitrous oxide reductase (N2OR) by Masha G. Savelieff, Yi Lu, and coworkers at the University of Illinois, Urbana-Champaign, now provide experimental evidence for that connection (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.0711316105). The researchers added copper to metal-free protein and observed by electronic absorption and electron paramagnetic resonance spectroscopy that copper was first incorporated almost equally in separate type 1 (blue) and type 2 (red) sites. Over time the separate sites converted to the binuclear CuA structure. “These observations suggest that the purple CuA site contains the essential elements of type 1 and type 2 copper centers” and provide insight into the evolutionary relationships among cupredoxin proteins, the authors write.
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