title: Eukaryotically encoded and chloroplast-located rubredoxin is associated with photosystem II.
abstract: We analyzed a eukaryotically encoded rubredoxin from the cryptomonad Guillardia theta and identified additional domains at the N- and C-termini in comparison to known prokaryotic paralogous molecules. The cryptophytic N-terminal extension was shown to be a transit peptide for intracellular targeting of the protein to the plastid, whereas a C-terminal domain represents a membrane anchor. Rubredoxin was identified in all tested phototrophic eukaryotes. Presumably facilitated by its C-terminal extension, nucleomorph-encoded rubredoxin (nmRub) is associated with the thylakoid membrane. Association with photosystem II (PSII) was demonstrated by co-localization of nmRub and PSII membrane particles and PSII core complexes and confirmed by comparative electron paramagnetic resonance measurements. The midpoint potential of nmRub was determined as +125 mV, which is the highest redox potential of all known rubredoxins. Therefore, nmRub provides a striking example of the ability of the protein environment to tune the redox potentials of metal sites, allowing for evolutionary adaption in specific electron transport systems, as for example that coupled to the PSII pathway.
authors.affiliation: Fachbereich Biologie, Philipps-Universität Marburg, Karl-von-Frisch-Strasse, D-35032 Marburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Wastl
authors.forename: E C
authors.initials: EC
authors.lastname: Duin
authors.forename: L
authors.initials: L
authors.lastname: Iuzzolino
authors.forename: W
authors.initials: W
authors.lastname: Dörner
authors.forename: T
authors.initials: T
authors.lastname: Link
authors.forename: S
authors.initials: S
authors.lastname: Hoffmann
authors.forename: H
authors.initials: H
authors.lastname: Sticht
authors.forename: H
authors.initials: H
authors.lastname: Dau
authors.forename: K
authors.initials: K
authors.lastname: Lingelbach
authors.forename: U G
authors.initials: UG
authors.lastname: Maier
mesh_terms: D001692:Biological Transport; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000235:genetics*; D002736:Chloroplasts / Q000737:chemistry* / Q000648:ultrastructure; D056890:Eukaryota / Q000737:chemistry / Q000648:ultrastructure; D005057:Eukaryotic Cells; D018532:Pisum sativum; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D045332:Photosystem II Protein Complex; D021382:Protein Sorting Signals; D012416:Rubredoxins / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D021382:Protein Sorting Signals; D012416:Rubredoxins