Genetic analysis of the Photosystem I subunits from the red alga, Galdieria sulphuraria

Christopher Vanselow, Andreas P M Weber, Kirsten Krause, Petra Fromme

Research output: Contribution to journalArticlepeer-review

44 Scopus citations


Currently, there are very little data available regarding the photosynthetic apparatus of red algae. We have analyzed the genes for Photosystem I in the recently sequenced genome of the red alga Galdieria sulphuraria. All subunits that are conserved between plants and cyanobacteria were unambiguously identified in the Galdieria genome: PsaA, PsaB, PsaC, PsaD, PsaE, PsaF, PsaI, PsaJ, PsaK and PsaL. From the plant specific subunits, PsaN and PsaO were identified but the sequence homology was much lower than for the subunits that are present in plants and cyanobacteria. The subunit PsaX, which is specific for thermophilic cyanobacteria, is not present in the Galdieria genome, whereas PsaM is a plastid-encoded protein as in other red algae. The sequences of the core subunits of PSI were further analyzed by mapping of the conserved areas in the crystal structures of cyanobacterial and plant PSI. The structural comparison shows that PSI from the red alga Galdieria may represent a common ancestral structure at the interface between cyanobacterial and plant PSI. Some subunits have a "zwitter" structure that contains structural elements that show similarities with either plant or cyanobacterial PSI. The structure of PsaL, which is responsible for the trimerization of PSI in cyanobacteria, lacks a short helix and the Ca2+ binding site, which are essential for trimer formation indicating that the Galdieria PSI is a monomer. However the sequence homology to plant PsaL is low and lacks strong conservation of the interaction sites with PsaH. Furthermore, the sites for interaction of plant PSI with the LHCI complex are not well conserved between plants and Galdieria, which may indicate that Galdieria may contain a PSI that is evolutionarily much more ancient than PSI from green algae, plants and the current cyanobacteria.

Original languageEnglish (US)
Pages (from-to)46-59
Number of pages14
JournalBiochimica et Biophysica Acta - Bioenergetics
Issue number1
StatePublished - Jan 2009


  • Electron transfer
  • Evolution
  • Gene identification
  • Light harvesting
  • Photosynthesis
  • Photosystem I
  • Red algae

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology


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