title: Thermostability and Ca2+ binding properties of wild type and heterologously expressed PsbO protein from cyanobacterial photosystem II.
abstract: Oxygenic photosynthesis takes place in the thylakoid membrane of cyanobacteria, algae, and higher plants. Initially light is absorbed by an oligomeric pigment-protein complex designated as photosystem II (PSII), which catalyzes light-induced water cleavage under release of molecular oxygen for the biosphere on our planet. The membrane-extrinsic manganese stabilizing protein (PsbO) is associated on the lumenal side of the thylakoids close to the redox-active (Mn)(4)Ca cluster at the catalytically active site of PSII. Recombinant PsbO from the thermophilic cyanobacterium Thermosynechococcus elongatus was expressed in Escherichia coli and spectroscopically characterized. The secondary structure of recombinant PsbO (recPsbO) was analyzed in the absence and presence of Ca(2+) using Fourier transform infrared spectroscopy (FTIR) and circular dichroism spectropolarimetry (CD). No significant structural changes could be observed when the PSII subunit was titrated with Ca(2+) in vitro. These findings are compared with data for spinach PsbO. Our results are discussed in the light of the recent 3D-structural analysis of the oxygen-evolving PSII and structural/thermodynamic differences between the two homologous proteins from thermophilic cyanobacteria and plants.
authors.affiliation: Department of Chemistry/Crystallography, Free University Berlin, 14195 Berlin, Germany. loll@chemie.fu-berlin.de
authors.forename: Bernhard
authors.initials: B
authors.lastname: Loll
authors.forename: Gisa
authors.initials: G
authors.lastname: Gerold
authors.forename: Daria
authors.initials: D
authors.lastname: Slowik
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Voelter
authors.forename: Christiane
authors.initials: C
authors.lastname: Jung
authors.forename: Wolfram
authors.initials: W
authors.lastname: Saenger
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Irrgang
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D002942:Circular Dichroism; D000458:Cyanobacteria; D041961:Deuterium Exchange Measurement; D006358:Hot Temperature; D045332:Photosystem II Protein Complex / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D017550:Spectroscopy, Fourier Transform Infrared; D018724:Spinacia oleracea
chemical_list: D001426:Bacterial Proteins; D002135:Calcium-Binding Proteins; D045332:Photosystem II Protein Complex; D021122:Protein Subunits; D011994:Recombinant Proteins; D002118:Calcium