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@PHDTHESIS{Klsch:888817,
      author       = {Kölsch, Adrian},
      title        = {{K}inetische, theoretische und strukturelle
                      {C}harakterisierung des {C}ytochrom c-{P}hotosystem
                      {I}-{K}omplexes},
      school       = {HU Berlin},
      type         = {Dissertation},
      reportid     = {FZJ-2020-05231},
      pages        = {139 p},
      year         = {2020},
      note         = {Dissertation, HU Berlin, 2020},
      abstract     = {Photosystem I (PSI) from the thermophilic cyanobacterium
                      Thermosynechococcus elongatus is a membrane-bound,
                      multipigment protein supercomplex. It converts light to
                      electrochemical energy with a quantum efficiency of almost
                      100 $\%.$ It reduces theluminal proteins plastocyanin and
                      cytochrome c6 (Cyt c6) to oxidize the stromalprotein
                      Ferredoxin. The structure of PSI has been solved in 2001 at
                      a resolution of 2,5 ˚A (Jordan et al. 2001). PSI can be
                      assembled on an electrode surface to produce photocurrents
                      and the generated electrons can be used for the production
                      of biofuels.The mitochondrial cytochrome c from horse heart
                      (Cyt cHH) binds strongly to both, PSI and the electrode
                      surface, and can therefore be applied to improve the
                      electrical coupling. Due to the practical use of the PSI-Cyt
                      c complex, the aim of my thesis isto characterize the
                      interaction of PSI with Cyt c6 and the analog Cyt cHH. To
                      this end, the binding of both cytochromes to PSI was
                      analyzed by kinetic, calorimetric, theory-based and
                      structural methods.Cyt c6 binds to PSI while being reduced
                      and decreases its affinity after transferring its electron.
                      In contrast, Cyt cHH binds to PSI in both oxidation states,
                      reduced and oxidized, with identical affinity. By means of
                      kinetic measurements, I identified condi-tions in which PSI
                      forms a stable complex with either of the two cytochromes.
                      The posi-tions of the cytochrome binding sites at PSI were
                      calculated by a rigid-body docking.For the calculation with
                      Cyt c6, the majority of the potential binding sites are
                      located at the luminal side of PSI, close to P700. The
                      theoretic properties of one of these bindingsites are in
                      good agreement with my own kinetic measurements and
                      literature data.The position and orientation of Cyt c6 in
                      this theoretic binding site is almost iden-tical to the
                      localization of Cyt c2 in cocrystals with the bacterial
                      reaction center from Rhodobacter sphaeroides. The potential
                      Cyt cHH binding sites are uniformly distri-buted over the
                      luminal surface of PSI. Still, cocrystals consisting of PSI
                      and Cyt cHH in a 1 : 1 ratio were produced. The crystal
                      structure was solved to a resolution of 3,4 ˚A,however, no
                      electron density corresponding to Cyt cHH was found. To
                      verify the PSI-Cyt c6 complex, the two proteins were
                      crosslinked and the structure was solved by cryo electron
                      microscopy (cryo-EM) to a resolution of 2,9 ˚A. No density
                      correspondingto Cyt c6 is present in the cryo-EM
                      reconstruction, but masked classification revealed3D
                      classes containing additional density at the luminal surface
                      of PSI. The cryo-EM structure reveals density of five
                      additional cofactors and the flexible subunit PsaK. For the
                      analysis of electron transport processes, serial femtosecond
                      crystallography (SFX) was used. Datasets were measured for
                      PSI crystals without cytochromes at resolutions of 2,75 ˚A
                      (oxidized), 3,4 ˚A (reduced, dark adapted) and 3,4 ˚A (100
                      ns after light flash).Additionally, a protocol for the
                      production of PSI-Cyt cHH cocrystals, suitable for the
                      measurement by the SFX-method, was designed. With the
                      crystal structure, the cryo-EM-structure and the
                      SFX-structure, three high resolution structures from the
                      same PSI-protein are now available. The differences between
                      these structures are discussed in respect to their
                      influence on the function of PSI.},
      cin          = {JCNS-FRM-II / MLZ},
      cid          = {I:(DE-Juel1)JCNS-FRM-II-20110218 / I:(DE-588b)4597118-3},
      pnm          = {6G4 - Jülich Centre for Neutron Research (JCNS) (POF3-623)
                      / 6G15 - FRM II / MLZ (POF3-6G15)},
      pid          = {G:(DE-HGF)POF3-6G4 / G:(DE-HGF)POF3-6G15},
      experiment   = {EXP:(DE-MLZ)KWS1-20140101},
      typ          = {PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/888817},
}