Covalent cross-linking of the Phytophthora megasperma oligopeptide elicitor to its receptor in parsley membranes.
An oligopeptide elicitor from Phytophthora megasperma f.sp. glycinea (Pep-13) that induces phytoalexin accumulation in cultured parsley cells was radioiodinated and chemically cross-linked to its binding site in microsomal and plasma membrane preparations with each of three homobifunctional reagents. Analysis by SDS/PAGE and autoradiography of solubilized membrane proteins demonstrated labeling of a 91-kDa protein, regardless of which reagent was used. Cross-linking of this protein was prevented by addition of excess unlabeled Pep-13. The competitor concentration found to half-maximally reduce the intensity of the cross-linked band was 6 nM, which is in good agreement with the IC50 value of 4.7 nM, obtained from ligand binding assays. No crosslinking of 125I-labeled Pep-13 was observed by using microsomal membranes from three other plant species, indicating species-specific occurrence of the binding site. Coupling of 125I-Pep-13 to the parsley 91-kDa protein required the same structural elements within the ligand as was recently reported for binding of 125I-Pep-13 to parsley microsomes, elicitor-induced stimulation of ion fluxes across the plasma membrane, the oxidative burst, the expression of defense-related genes, and phytoalexin production. These findings suggest that the 91-kDa protein identified in parsley membranes is the oligopeptide elicitor receptor mediating activation of a multicomponent defense response.
Nürnberger
T
T
Max-Planck-Institut für Züchtungsforschung, Abteilung Biochemie, Cologne, Germany.
Nennstiel
D
D
Hahlbrock
K
K
Scheel
D
D
D000595:Amino Acid Sequence; D001667:Binding, Competitive; D002478:Cells, Cultured; D003432:Cross-Linking Reagents / Q000494:pharmacology; D018552:Daucus carota / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005656:Fungal Proteins / Q000302:isolation & purification / Q000378:metabolism*; D006023:Glycoproteins; D007425:Intracellular Membranes / Q000378:metabolism; D007457:Iodine Radioisotopes; D007700:Kinetics; D019684:Magnoliopsida / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000302:isolation & purification / Q000378:metabolism*; D008565:Membrane Proteins; D008861:Microsomes / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D010838:Phytophthora / Q000378:metabolism*; D010936:Plant Extracts / Q000096:biosynthesis; D012717:Sesquiterpenes; D013025:Glycine max / Q000378:metabolism; D013379:Substrate Specificity; D013388:Succinimides / Q000494:pharmacology*; D013729:Terpenes; D000094162:Phytoalexins
D003432:Cross-Linking Reagents; D005656:Fungal Proteins; D006023:Glycoproteins; D007457:Iodine Radioisotopes; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D010936:Plant Extracts; D012717:Sesquiterpenes; D013388:Succinimides; D013729:Terpenes; C091510:elicitor protein, Phytophthora megasperma; C011240:dithiobis(succinimidylpropionate); D000094162:Phytoalexins