Azido Auxins: Synthesis and Use as Photoaffinity Labeling Agents
Jones-Roche, Alan Monte
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https://hdl.handle.net/2142/71275
Description
Title
Azido Auxins: Synthesis and Use as Photoaffinity Labeling Agents
Author(s)
Jones-Roche, Alan Monte
Issue Date
1984
Department of Study
Plant Biology
Discipline
Plant Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Botany
Abstract
A technique to isolate auxin-binding proteins in plants was developed. Three analogs of indole-3-acetic acid, a natural plant hormone of the class called auxins, were synthesized by Dr. Lee Melhado to be used as photoaffinity labeling agents in plants. The analogs, 4-, 5-, and 6-azidoindole-3-acetic acid, were prepared in seven steps with overall yields of 2-20%. The nonfluorescent analogs are stable in the dark but degrade to fluorescent products upon photolysis. The analogs were tested for biological activity in eight plant systems, and they induce cell elongation, cell division, and were polarly transported at rates comparable to indole-3-acetic acid. 4-Azido-3-acetic acid has a unique property in soybean. When soybean tissue, preincubated with 4-azidoindole-3-acetic acid, is irradiated with ultraviolet light, they lose the requirement of exogenous auxin for cell elongation. This result, together with results of other experiments, suggests that 4-azidoindole-3-acetic acid becomes covalently attached to the auxin receptor and thus permanently induces growth. The 4- and 5-isomers, but not the 6-isomer or the photoproducts of 5-azido-3-acetic acid, compete for napthaleneacetic acid binding in maize with affinities equal to or better, than affinities for indole-3-acetic acid binding. Auxin-binding sites, pretreated with 5-azidoindole-3-acetic acid and ultraviolet light, become specifically labeled. Tritiated 5-azidoindole-3-acetic acid was used to label auxin-binding proteins in a microsomal fraction prepared from maize. Proteins which bind indole-3-acetic acid, but not napthalene-1-acetic acid, migrate as four bands in sodium dodecylsulfate polyacrylamide electrophoresis with apparent molecular weights of 60, 49, 45, and 37 kilodaltons. These proteins focus as at least five bands in isoelectric focusing gels with apparent isoelectric points of 4.8, 5.0, 5.1, 5.2, and 5.3. Results of additional experiments suggest that these proteins are involved in auxin transport.
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