Preparation of the Oxidized and Reduced Forms of Psoriasin (S100A7)

  • Lisa S. Cunden
  • Elizabeth M. NolanEmail author
Part of the Methods in Molecular Biology book series (MIMB, volume 1929)


Human S100A7 (psoriasin) is a metal-chelating host-defense protein expressed by epithelial cells. S100A7 possesses two Cys residues that generate two redox isoforms of the protein. In the oxidized form (S100A7ox), Cys47 and Cys96 form an intramolecular disulfide bond, whereas these residues exist as free thiols in the reduced form (S100A7red). In this chapter, we provide a step-by-step protocol for the purification of S100A7ox and S100A7red that affords each protein in high yield and purity. In this procedure, S100A7 is expressed in Escherichia coli BL21(DE3), and the homodimer is obtained following ammonium sulfate precipitation, folding, and column chromatography. Treatment of S100A7 with 1,4-dithiothreitol (DTT) affords S100A7red. A Cu(II)-catalyzed oxidation reaction is employed to obtain S100A7ox. A RP-HPLC method that allows for baseline separation of S100A7ox and S100A7red is provided, as well as a biochemical Zn(II)-binding assay that can be employed to evaluate the functional integrity of S100A7.

Key words

S100 protein EF-hand Bacterial expression Zn(II)-binding protein Disulfide bond 



Our current studies of psoriasin are supported by the National Science Foundation (CHE-1352132).


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© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of ChemistryMassachusetts Institute of TechnologyCambridgeUSA

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