title: Molecular Analysis and Localization of CaARA7 a Conventional RAB5 GTPase from Characean Algae.
abstract: RAB5 GTPases are important regulators of endosomal membrane traffic. Among them Arabidopsis thaliana ARA7/RABF2b is highly conserved and homologues are present in fungal, animal and plant kingdoms. In land plants ARA7 and its homologues are involved in endocytosis and transport towards the vacuole. Here we report on the isolation of an ARA7 homologue (CaARA7/CaRABF2) in the highly evolved characean green alga Chara australis. It encodes a polypeptide of 202 amino acids with a calculated molecular mass of 22.2 kDa and intrinsic GTPase activity. Immunolabelling of internodal cells with a specific antibody reveals CaARA7 epitopes at multivesicular endosomes (MVEs) and at MVE-containing wortmannin (WM) compartments. When transiently expressed in epidermal cells of Nicotiana benthamiana leaves, fluorescently tagged CaARA7 localizes to small organelles (putative MVEs) and WM compartments, and partially colocalizes with AtARA7 and CaARA6, a plant specific RABF1 GTPase. Mutations in membrane anchoring and GTP binding sites alter localization of CaARA7 and affect GTPase activity, respectively. This first detailed study of a conventional RAB5 GTPase in green algae demonstrates that CaARA7 is similar to RAB5 GTPases from land plants and other organisms and shows conserved structure and localization.
authors: Department of Cell Biology/Plant Physiology, University of Salzburg, Hellbrunnerstrasse 34, 5020, Salzburg, Austria.
authors: Marion C
authors: MC
authors: Hoepflinger
authors: Anja
authors: A
authors: Geretschlaeger
authors: Aniela
authors: A
authors: Sommer
authors: Margit
authors: M
authors: Hoeftberger
authors: Christina
authors: C
authors: Hametner
authors: Takashi
authors: T
authors: Ueda
authors: Ilse
authors: I
authors: Foissner
mesh_terms: D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D044522:Characeae / Q000201:enzymology* / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D008969:Molecular Sequence Data; D010802:Phylogeny; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics; D017354:Point Mutation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D020418:Algal Proteins; D029681:Arabidopsis Proteins; C495672:Ara7 protein, Arabidopsis; D020691:rab GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins
keywords: ARA7; Chara australis; RAB5 GTPase; RABF2; endosomal trafficking; multivesicular endosome
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