Auxin binding to corn coleoptile membranes: Kinetics and specificity

Abstract

Detailed examination of binding over the range 10(-7)-10(-6) M suggests that membrane preparations from coleoptiles of Zea mays L., cv Kelvedon 33 contain at least two sets of high affinity binding sites for 1-naphthylacetic acid (NAA), with dissociation constants of 1.8×10(-7) M (site 1) and 14.5×10(-7) M (site 2). Similar studies with 3-indolylacetic acid (IAA) also indicate two sets of binding sites, whose concentrations are closely comparable to those deduced for NAA. A substantial proportion of the total binding activity is retained in a detergent-solubilized preparation. Using [(14)C]NAA the interactions of a range of analogues with each of the binding sites have been examined with the aid of double reciprocal plots. The specificity of site 2 is compatible with that expected for an auxin receptor, in that only active auxins, antiauxin transport inhibitors are able to compete with [(14)C]NAA for the binding sites. Site 1 on the other hand is less specific, since it appears to bind all compounds tested, including physiologically inactive analogues.

Characterization of Naphthaleneacetic Acid Binding to Receptor Sites on Cellular Membranes of Maize Coleoptile Tissue

“…Figure 10 shows that although NAA binding is markedly reduced by low concentrations of supernatant, the effect of SF increases only up to a plateau at which a definite proportion of the specific NAA binding remains. This shows that SF is not endogenous native auxin (IAA) present in the supernatant, because IAA can displace NAA completely from the specific binding sites (2,9).…”

“…Various compounds structurally related to NAA, most notably IAA, displace NAA from saturable NAA-binding sites, with features that are as expected if the analogs compete with NAA for the same binding sites (2). Kinetics of competition by analogs for the NAA-binding sites will be described in detail separately (Ray, Dohrmann, and Hertel, in preparation).…”

ABP1 is required for organized cell elongation and division in Arabidopsis embryogenesis

“…However, the receptor(s) mediating any auxin action is unclear. The best known candidate for an auxin receptor mediating auxin-regulated cell expansion is auxin-binding protein 1 (ABP1), discovered 25 years ago (Batt et al 1976;Ray et al 1977) and characterized extensively since then. ABP1 is a low abundance protein found predominantly within the endoplasmic reticulum only in cells of aerial tissues that have the capacity to expand by auxin.…”

Properties of a Solubilized Microsomal Auxin-binding Protein from Coleoptiles and Primary Leaves of Zea mays

“…Natural and synthetic auxin have, in fact, been found to bind to sites in the microsomal membranes of Zea mays (2,(17)(18)(19). Furthermore, these auxins are bound with relative affmities roughly correlated to their ability to produce shoot elongation in the same tissue (2,19).…”

“…Natural and synthetic auxin have, in fact, been found to bind to sites in the microsomal membranes of Zea mays (2,(17)(18)(19). Furthermore, these auxins are bound with relative affmities roughly correlated to their ability to produce shoot elongation in the same tissue (2,19). These sites are most concentrated in microsomes of coleoptiles and primary leaves (which respond to auxin by elongation), while ' 3 Please address requests for reprints to this author.…”