title: Proteomic Analysis of a Fraction with Intact Eyespots of Chlamydomonas reinhardtii and Assignment of Protein Methylation.
abstract: Flagellate green algae possess a visual system, the eyespot. In Chlamydomonas reinhardtii it is situated at the edge of the chloroplast and consists of two carotenoid rich lipid globule layers subtended by thylakoid membranes (TM) that are attached to both chloroplast envelope membranes and a specialized area of the plasma membrane (PM). A former analysis of an eyespot fraction identified 203 proteins. To increase the understanding of eyespot related processes, knowledge of the protein composition of the membranes in its close vicinity is desirable. Here, we present a purification procedure that allows isolation of intact eyespots. This gain in intactness goes, however, hand in hand with an increase of contaminants from other organelles. Proteomic analysis identified 742 proteins. Novel candidates include proteins for eyespot development, retina-related proteins, ion pumps, and membrane-associated proteins, calcium sensing proteins as well as kinases, phosphatases and 14-3-3 proteins. Methylation of proteins at Arg or Lys is known as an important posttranslational modification involved in, e.g., signal transduction. Here, we identify several proteins from eyespot fractions that are methylated at Arg and/or Lys. Among them is the eyespot specific SOUL3 protein that influences the size and position of the eyespot and EYE2, a protein important for its development.
authors.affiliation: Cell Biology, Department of Biology, Friedrich-Alexander-University Erlangen-Nuremberg Erlangen, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Eitzinger
authors.affiliation: Institute of General Botany and Plant Physiology, Faculty of Biology and Pharmacy, Friedrich Schiller University Jena Jena, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Wagner
authors.affiliation: Institute of General Botany and Plant Physiology, Faculty of Biology and Pharmacy, Friedrich Schiller University Jena Jena, Germany.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Weisheit
authors.affiliation: Cell Biology and Electron Microscopy, University of Bayreuth Bayreuth, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Geimer
authors.affiliation: Cell Biology, Department of Biology, Friedrich-Alexander-University Erlangen-Nuremberg Erlangen, Germany.
authors.forename: David
authors.initials: D
authors.lastname: Boness
authors.affiliation: Cell Biology, Department of Biology, Friedrich-Alexander-University Erlangen-Nuremberg Erlangen, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Kreimer
authors.affiliation: Institute of General Botany and Plant Physiology, Faculty of Biology and Pharmacy, Friedrich Schiller University Jena Jena, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Mittag
keywords: ATP synthase; Chlamydomonas reinhardtii; EYE2; SOUL heme-binding protein 3; eyespot proteome; phototaxis; protein methylation