title: Gibberellin-photoaffinity labelling of two polypeptides in plant plasma membranes.
abstract: Two polypeptides of M(r) 68 kDa and 18 kDa were gibberellin (GA)-photoaffinity labelled in vitro in plasma membrane preparations from oat (Avena sativa L.) aleurone and from leaves and stems of wild-type and GA-sensitivity mutants of different species. Labelling of these polypeptides could be competed by biologically active, but not by inactive, GAs, indicating the likely biological significance of these interactions. On 2-dimensional gels the radiolabelled polypeptides were each resolved as one intensely labelled low abundance spot with a slightly lower pl form adjacent to it. There was a strong pH dependency for both labelling events, which correlated well with pH values at which GA are known to be most biologically active. A semi-dwarf GA-sensitivity mutant of sweet pea (Lathyrus odoratus L.), lb, showed reduced photoaffinity labelling of both polypeptides compared with the wild type, Lb. In the GA-insensitive Arabidopsis thaliana mutant gai, the level of labelling was the same as in wild type, GAI. This is the first report of GA-binding proteins in plant plasma membranes. Some preliminary sequence data are given for one of the labelled polypeptides. We discuss these mutants and consider their possible roles in GA perception or action.
authors.affiliation: IACR-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, UK.
authors.forename: A
authors.initials: A
authors.lastname: Lovegrove
authors.forename: D H
authors.initials: DH
authors.lastname: Barratt
authors.forename: M H
authors.initials: MH
authors.lastname: Beale
authors.forename: R
authors.initials: R
authors.lastname: Hooley
mesh_terms: D000345:Affinity Labels; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D018554:Avena / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015415:Biomarkers; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004351:Drug Resistance / Q000235:genetics; D015180:Electrophoresis, Gel, Two-Dimensional; D005875:Gibberellins / Q000378:metabolism* / Q000494:pharmacology; D005964:Glucosyltransferases / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D009154:Mutation; D018532:Pisum sativum / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism; D010940:Plant Proteins / Q000302:isolation & purification / Q000378:metabolism*; D010944:Plants / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins
chemical_list: D000345:Affinity Labels; D015415:Biomarkers; D002352:Carrier Proteins; D005875:Gibberellins; D008565:Membrane Proteins; D010750:Phosphoproteins; D010940:Plant Proteins; D029702:Schizosaccharomyces pombe Proteins; C099131:gibberellin-binding phosphoprotein, plant; D005964:Glucosyltransferases; C020570:1,3-beta-glucan synthase