title: The ethylene response mediator ETR1 from Arabidopsis forms a disulfide-linked dimer.
abstract: Mutations in the ETR1 gene of the higher plant Arabidopsis confer insensitivity to ethylene, indicating a role for the gene product in ethylene signal perception and transduction. The ETR1 gene product has an amino-terminal hydrophobic domain and a carboxyl-terminal domain showing homology to the two-component signal transduction proteins of bacteria. We report here that in both its native Arabidopsis and when transgenically expressed in yeast, the ETR1 protein is isolated from membranes as a dimer of 147 kDa. Treatment with the reducing agent dithiothreitol converted the dimer to a monomer of 79 kDa, indicative of a disulfide linkage between monomers. Expression of truncated versions of ETR1 in yeast confirmed that the high molecular mass form is a homodimer and demonstrated that the amino-terminal region of ETR1 is necessary and sufficient for this dimerization. Site-directed mutagenesis of two cysteines near the amino terminus of ETR1 prevented formation of the covalently linked dimer in yeast, consistent with a role in disulfide bond formation. These data indicate that ETR1 may use a dimeric mechanism of signal transduction in a manner similar to its bacterial counterparts but with the additional feature of a disulfide bond between monomers.
authors.affiliation: Department of Botany, University of Wisconsin, Madison 53706, USA.
authors.forename: G E
authors.initials: GE
authors.lastname: Schaller
authors.forename: A N
authors.initials: AN
authors.lastname: Ladd
authors.forename: M B
authors.initials: MB
authors.lastname: Lanahan
authors.forename: J M
authors.initials: JM
authors.lastname: Spanbauer
authors.forename: A B
authors.initials: AB
authors.lastname: Bleecker
mesh_terms: D017360:Arabidopsis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002458:Cell Fractionation; D003545:Cysteine / Q000235:genetics; D004220:Disulfides / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics; D005030:Ethylenes / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D017384:Sequence Deletion; D015398:Signal Transduction; D015003:Yeasts / Q000235:genetics
chemical_list: D004220:Disulfides; D005030:Ethylenes; D008565:Membrane Proteins; D010940:Plant Proteins; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; C083750:ethylene receptors, plant; C036216:ethylene; D003545:Cysteine