The auxin-binding pocket of auxin-binding protein 1 comprises the highly conserved boxes a and c.
The auxin-binding protein 1 (ABP1) has already been proved to be an extracellular receptor of auxin in single cell systems. Protoplasts of maize coleoptiles respond to auxin with an increase in volume. The 2-naphthaleneacetic acid (2-NAA), an inactive auxin analog, acts as an anti-auxin in protoplast swelling, as it suppresses the effect of indole-3-acetic acid (IAA). Antibodies raised against box a of ABP1 induce protoplast swelling in the absence of auxin. This response is inhibited by pre-incubation with 2-NAA. The effect of 2-NAA on swelling induced by agonistic antibodies appears to depend on the binding characteristics of the antibody. ScFv12, an antibody directed against box a, box c and the C-terminal domain of ABP1 also exhibits auxin-agonist activity which is, however, not abolished by 2-NAA. Neither does 2-NAA affect the activity of the C-terminal peptide of ABP1, which is predicted to interact with putative binding proteins of ABP1. These results support the view that box a and box c of ABP1 are auxin-binding domains.
Dahlke
Renate I
RI
Botanisches Institut und Botanischer Garten der Christian-Albrechts-Universität zu Kiel, 24118 Kiel, Germany.
Lüthen
Hartwig
H
Steffens
Bianka
B
D000906:Antibodies / Q000494:pharmacology; D001665:Binding Sites; D001667:Binding, Competitive / Q000187:drug effects; D001681:Biological Assay; D017124:Conserved Sequence; D007128:Immunoglobulin Fragments / Q000276:immunology; D007210:Indoleacetic Acids / Q000378:metabolism* / Q000494:pharmacology; D009280:Naphthaleneacetic Acids / Q000494:pharmacology; D010455:Peptides / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism*; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000378:metabolism*; D003313:Zea mays / Q000187:drug effects / Q000378:metabolism*
D000906:Antibodies; D007128:Immunoglobulin Fragments; D007210:Indoleacetic Acids; D009280:Naphthaleneacetic Acids; D010455:Peptides; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C083846:auxin-binding protein 1; C030737:indoleacetic acid