title: Function of PsbO, the photosystem II manganese-stabilizing protein: probing the role of aspartic acid 157.
abstract: The D157N, D157E, and D157K mutations in the psbO gene encoding the photosystem II (PSII) manganese-stabilizing protein from spinach, exhibit near-wild-type PSII binding but are significantly impaired in O(2) evolution activity and Cl(-) retention by PSII [Popelkova et al. (2009) Biochemistry 48, 11920-11928]. To better characterize the role of PsbO-Asp157 in eukaryotic PSII, the effect of mutations in Asp157 on heat-induced changes in PsbO solution structure, O(2) release kinetics, and PSII redox reactions both within and outside the oxygen-evolving complex (OEC) have been examined. The data presented here show that Asn, Glu, or Lys mutations in PsbO-Asp157 modify PsbO thermostability in solution, which is consistent with the previously reported perturbation of the functional assembly of PsbO-Asp157 mutants into PSII that caused inefficient Cl(-) retention by PSII. Fluorescence decay signals from PSII reconstituted with Asp157 mutants indicate that that the Q(A)(-) to Q(B) transition on the PSII reducing side is unaffected, but complex alterations are detected on the PSII oxidizing side that affect the recombination of Q(A)(-) with the O(2)-evolving complex. In addition, oxygen yield on the first flash is increased, which indicates an impaired ability of mutant-reconstituted PSII samples to decay back to the S(1) state in the dark.
authors.affiliation: Department of Biological Sciences, Division of Biochemistry and Molecular Biology, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: Johnna L
authors.initials: JL
authors.lastname: Roose
authors.forename: Charles F
authors.initials: CF
authors.lastname: Yocum
authors.forename: Hana
authors.initials: H
authors.lastname: Popelkova
mesh_terms: D001224:Aspartic Acid / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004795:Enzyme Stability; D005453:Fluorescence; D006358:Hot Temperature; D009154:Mutation; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D018724:Spinacia oleracea / Q000201:enzymology*
chemical_list: D045332:Photosystem II Protein Complex; D010940:Plant Proteins; C052389:oxygen-evolving enhancer protein 1, plant; C054266:photosystem II manganese-stabilizing protein; D001224:Aspartic Acid