Auxin binding protein

Henderson J, Bauly JM, Ashford DA, Oliver SC, Hawes CR, Lazarus CM, Venis MA, Napier RM. Retention of maize auxin-binding protein in the endoplasmic reticulum quantifying escape and the role of auxin. Planta 1997 202 313-323. 

Napier, R. M., and M. A. Venis, From auxin-binding protein to plant hormone receptor Trends Biochem. Sci. 16 72— 75, 1991. 

Napier, R.M. Venis, M.A. (1993). Tansley Review No. 79. Auxin action and auxin binding proteins. New Phytol. 129, 167-201. 

Palme, K., Feldwisch, J., Peters, W.S., Schell, J., Zettl, R., Campos, N., Felle, H. (1992). Auxin binding proteins are located in the ER and in the plasma membrane Identification by photoaffinity-labelling and characterization. Progress in Plant Growth Regulation (Karssen, C.M., Van Loon, L.C., Vreugdenhil, D., Eds.), pp. 73-81. Kluwer Academic, The Netherlands. 

Auxin Binding Protein Receptor 1LR5 His 1 HiSj 3 Glu 42 His H20... 

ABP Auxin binding protein MeJA Methyl jasmonate... 

There are three major classes of synthetic auxins the aryl acetic acids, which include indoleacetic acid (lAA) itself (Fig. 1 structure 2-1) and 1-naphthyl acetic acid (2-4), phenoxy acetic acids, represented by 2,4-dichlorophenoxy acetic acid (2,4-D) (2-7) and the benzoic acids, e.g. 2,3,6-trichloro benzoic acid (2-9). It remains the case however, that there is no stmcture-activity proposal which satisfactorily covers all molecules which are known to have auxin activity. As is well known, auxins have multiple effects, including promotion of cell elongation, cell division and gene expression. There may well be different receptors for each effect, and differences between receptors. An auxin binding protein (ABP), has now been characterised, and is possibly a receptor controlling cell elongation [3]. 

ABP auxin binding protein GAP GTPase activating protein... 

Several auxin-binding proteins (ABPs, 20,000-22,000) have been identified. These small proteins are characterized by the presence of an auxin-binding motif, a glycosylation site, and the carboxy-terminal sequence -Lys-Asp-Glu-Leu-COOH. At least 5 ABPs are present in Zea mays. In the Baculovirus expression systetrt, Zea ABPl (ZrnABPl) is targeted to the endoplasmic reticulum of the insect cells used for... 

Similar results were obtained using two partially purified (by chroma-tofocusing) auxin-binding proteins from pea-epicotyls [1, 2]. Both proteins stimulated transcription in isolated pea nuclei in the presence of 10 M lAA [3]. They also isolated two auxin-binding proteins from soybean cell suspensions with similar characteristics, although to date no influence on transcription has been demonstrated [3]. 

On the other hand, Sakai [11] and Sakai and Hanagate [12] partially purified two auxin-binding proteins from mung bean by affinity chromatography. Both proteins stimulated RNA-synthesis (24-39%) in isolated mung bean hypocotyls, but neither protein required lAA for this stimulatory effect [13]. 

Further differences lie in the reported affinities for the auxin-binding proteins K(j for tobacco is 6 X 10 M [ 15] K s for pea are 10 M and 6 X 10 M [3] while K s for mung bean are 3X 10 M [12] and 10" M [11]. The latter values represent affinities that are 50- to 500-fold lower than for pea and tobacco material. We therefore think it is premature to consider the auxin-binding proteins from mung bean as true receptors. 

The next step in the perception-transduction mechanism of auxin should be more specific. We plan to use the reinitiating nuclei from tobacco in reconstitution experiments with partially purified auxin-binding protein. We have shown in vivo that several genes are specifically induced by auxin. We hope to be able to show the same induction in vitro by addition of auxin-receptor complex to nuclei isolated from auxin-starved cells, where these genes are normally not expressed. 

Without doubt, auxin binding sites in maize membranes have been studied the most extensively in a number of laboratories. Several lines of correlative evidence suggest that the sites have a receptor function [21 ] as do the more direct observations of inhibition of auxin-induced growth by an affinity-purified antibody to the auxin binding protein [12] and functional reconstitution of binding protein and ATPase in a bilayer lipid membrane [18]. The binding sites can be readily solubilized from the membranes using an acetone procedure and a native Mr of 40-45 kDa is obtained on gel filtration [19]. 

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