title: Importance of a single disulfide bond for the PsbO protein of photosystem II: protein structure stability and soluble overexpression in Escherichia coli.
abstract: PsbO protein is an important constituent of the water-oxidizing complex, located on the lumenal side of photosystem II. We report here the efficient expression of the spinach PsbO in E. coli where the solubility depends entirely on the formation of the disulfide bond. The PsbO protein purified from a pET32 system that includes thioredoxin fusion is properly folded and functionally active. Urea unfolding experiments imply that the reduction of the single disulfide bridge decreases stability of the protein. Analysis of inter-residue contact density through the PsbO molecule shows that Cys51 is located in a cluster with high contact density. Reduction of the Cys28-Cys51 bond is proposed to perturb the packing interactions in this cluster and destabilize the protein as a whole. Taken together, our results give evidence that PsbO exists in solution as a compact highly ordered structure, provided that the disulfide bridge is not reduced.
authors: Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, 901 87 Umea, Sweden.
authors: Julia
authors: J
authors: Nikitina
authors: Tatiana
authors: T
authors: Shutova
authors: Bogdan
authors: B
authors: Melnik
authors: Sergey
authors: S
authors: Chernyshov
authors: Victor
authors: V
authors: Marchenkov
authors: Gennady
authors: G
authors: Semisotnov
authors: Vyacheslav
authors: V
authors: Klimov
authors: Göran
authors: G
authors: Samuelsson
mesh_terms: D004220:Disulfides; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012995:Solubility; D018724:Spinacia oleracea / Q000737:chemistry; D013879:Thioredoxins / Q000378:metabolism
chemical_list: D004220:Disulfides; D045332:Photosystem II Protein Complex; D011994:Recombinant Proteins; C054266:photosystem II manganese-stabilizing protein; D013879:Thioredoxins