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@ARTICLE{Oberleitner:888273,
      author       = {Oberleitner, Linda and Poschmann, Gereon and Macorano, Luis
                      and Schott-Verdugo, Stephan and Gohlke, Holger and Stühler,
                      Kai and Nowack, Eva C. M.},
      title        = {{T}he {P}uzzle of {M}etabolite {E}xchange and
                      {I}dentification of {P}utative {O}ctotrico {P}eptide
                      {R}epeat {E}xpression {R}egulators in the {N}ascent
                      {P}hotosynthetic {O}rganelles of {P}aulinella chromatophora},
      journal      = {Frontiers in microbiology},
      volume       = {11},
      issn         = {1664-302X},
      address      = {Lausanne},
      publisher    = {Frontiers Media},
      reportid     = {FZJ-2020-04800},
      pages        = {607182},
      year         = {2020},
      abstract     = {The endosymbiotic acquisition of mitochondria and plastids
                      more than one billion years ago was central for the
                      evolution of eukaryotic life. However, owing to their
                      ancient origin, these organelles provide only limited
                      insights into the initial stages of organellogenesis. The
                      cercozoan amoeba Paulinella chromatophora contains
                      photosynthetic organelles—termed chromatophores—that
                      evolved from a cyanobacterium ∼100 million years ago,
                      independently from plastids in plants and algae. Despite the
                      more recent origin of the chromatophore, it shows tight
                      integration into the host cell. It imports hundreds of
                      nucleus-encoded proteins, and diverse metabolites are
                      continuously exchanged across the two chromatophore envelope
                      membranes. However, the limited set of chromatophore-encoded
                      solute transporters appears insufficient for supporting
                      metabolic connectivity or protein import. Furthermore,
                      chromatophore-localized biosynthetic pathways as well as
                      multiprotein complexes include proteins of dual genetic
                      origin, suggesting that mechanisms evolved that coordinate
                      gene expression levels between chromatophore and nucleus.
                      These findings imply that similar to the situation in
                      mitochondria and plastids, also in P. chromatophora nuclear
                      factors evolved that control metabolite exchange and gene
                      expression in the chromatophore. Here we show by mass
                      spectrometric analyses of enriched insoluble protein
                      fractions that, unexpectedly, nucleus-encoded transporters
                      are not inserted into the chromatophore inner envelope
                      membrane. Thus, despite the apparent maintenance of its
                      barrier function, canonical metabolite transporters are
                      missing in this membrane. Instead we identified several
                      expanded groups of short chromatophore-targeted orphan
                      proteins. Members of one of these groups are characterized
                      by a single transmembrane helix, and others contain
                      amphipathic helices. We hypothesize that these proteins are
                      involved in modulating membrane permeability. Thus, the
                      mechanism generating metabolic connectivity of the
                      chromatophore fundamentally differs from the one for
                      mitochondria and plastids, but likely rather resembles the
                      poorly understood mechanism in various bacterial
                      endosymbionts in plants and insects. Furthermore, our mass
                      spectrometric analysis revealed an expanded family of
                      chromatophore-targeted helical repeat proteins. These
                      proteins show similar domain architectures as known
                      organelle-targeted expression regulators of the octotrico
                      peptide repeat type in algae and plants. Apparently these
                      chromatophore-targeted proteins evolved convergently to
                      plastid-targeted expression regulators and are likely
                      involved in gene expression control in the chromatophore.},
      cin          = {IBI-7 / JSC / NIC},
      ddc          = {570},
      cid          = {I:(DE-Juel1)IBI-7-20200312 / I:(DE-Juel1)JSC-20090406 /
                      I:(DE-Juel1)NIC-20090406},
      pnm          = {511 - Computational Science and Mathematical Methods
                      (POF3-511) / Forschergruppe Gohlke $(hkf7_20200501)$},
      pid          = {G:(DE-HGF)POF3-511 / $G:(DE-Juel1)hkf7_20200501$},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {33329499},
      UT           = {WOS:000597304700001},
      doi          = {10.3389/fmicb.2020.607182},
      url          = {https://juser.fz-juelich.de/record/888273},
}