title: A conserved domain of the arabidopsis GNOM protein mediates subunit interaction and cyclophilin 5 binding.
abstract: The Arabidopsis GNOM protein, a guanine nucleotide exchange factor (GEF) that acts on ADP ribosylation factor (ARF)-type G proteins, is required for coordination of cell polarity along the apical-basal embryo axis. Interallelic complementation of gnom mutants suggested that dimerization is involved in GNOM function. Here, direct interaction between GNOM molecules is demonstrated in vitro and by using a yeast two-hybrid system. Interaction was confined to an N-terminal domain conserved within a subgroup of large ARF GEFs. The same domain mediated in vitro binding to cyclophilin 5 (Cyp5), which was identified as a GNOM interactor in two-hybrid screening. Cyp5 displayed peptidylprolyl cis/trans-isomerase and protein refolding activities that were sensitive to cyclosporin A. Cyp5 protein accumulated in several plant organs and, like GNOM, was partitioned between cytosolic and membrane fractions. Cyp5 protein was also expressed in the developing embryo. Our results suggest that Cyp5 may regulate the ARF GEF function of the GNOM protein during embryogenesis.
authors.affiliation: Entwicklungsgenetik, Zentrum für Molekularbiologie der Pflanzen, Universität Tübingen, Auf der Morgenstelle 1, D-72076 Tübingen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Grebe
authors.forename: J
authors.initials: J
authors.lastname: Gadea
authors.forename: T
authors.initials: T
authors.lastname: Steinmann
authors.forename: M
authors.initials: M
authors.lastname: Kientz
authors.forename: J U
authors.initials: JU
authors.lastname: Rahfeld
authors.forename: K
authors.initials: K
authors.lastname: Salchert
authors.forename: C
authors.initials: C
authors.lastname: Koncz
authors.forename: G
authors.initials: G
authors.lastname: Jürgens
mesh_terms: D020727:ADP-Ribosylation Factors / Q000737:chemistry / Q000235:genetics; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002384:Catalysis / Q000187:drug effects; D017124:Conserved Sequence; D016572:Cyclosporine / Q000494:pharmacology; D019281:Dimerization; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D019696:Peptidylprolyl Isomerase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000254:growth & development / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D016572:Cyclosporine; D020727:ADP-Ribosylation Factors; D019696:Peptidylprolyl Isomerase