A soluble auxin-binding protein from Hyoscyamus muticus is a glutathione S-transferase.
We have used the photoaffinity label azido-[3H]IAA (5-N3-[7-3H]indole-3-acetic acid), a biologically active analog of indole-3-acetic acid, to identify auxin-binding proteins (ABPs) in the soluble fraction of Hyoscyamus muticus. A 25-kD polypeptide previously described (H. Macdonald, A. M. Jones, P. J. King [1991] J Biol Chem 266: 7393-7399) has now been purified to homogeneity by conventional methods. Binding of azido-[3H]IAA to the purified protein was reduced by active auxins but not by inactive indoles. Partial amino acid sequences of the purified protein showed high homology to glutathione S-transferase (GST) from tobacco (ParB) and from maize (GT32). The conclusion that the 25-kD ABP is a GST is further supported by high GST activity in fractions highly enriched in the 25-kD polypeptide and recognition of the ABP by antibodies against GST from wheat and maize. Furthermore, purification of a protein from a soluble protein extract from H. muticus by affinity chromatography on glutathione-agarose also yielded a 25-kD polypeptide that was indistinguishable in its N-terminal amino acid sequence and biochemical characteristics from the protein purified by conventional methods. Possible functions of GST in auxin action are discussed.
Bilang
J
J
Friedrich Miescher-Institut, Basel, Switzerland.
Macdonald
H
H
King
P J
PJ
Sturm
A
A
D000595:Amino Acid Sequence; D001386:Azides / Q000378:metabolism; D001667:Binding, Competitive; D002846:Chromatography, Affinity; D005982:Glutathione Transferase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism*; D008969:Molecular Sequence Data; D010937:Plant Growth Regulators; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010944:Plants / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D001386:Azides; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C046131:auxin receptor, plant; C068520:5-azido-1H-indole-3-acetic acid; D005982:Glutathione Transferase