Azido Auxins

Publisher Website
Google Scholar
Abstract
Tritiated 5-azidoindole-3-acetic acid (5-N3-[7-3H]IAA), a photoaffinity labeling agent, was used to photolabel proteins of a crude microsomal preparation from maize (Z. mays L., ''Bear Hybrid'', WF9 .times. BR38) coleoptile. Approximately 50% of the bound radioactivity was solubilized in 5 M urea containing Triton X-100, and the extract was fractionated using a variety of techniques. High performance liquid chromatography demonstrated that, although many membrane proteins incorporated tritiated label, only a few showed reduced incorporation in the presence of excess IAA. No detectable reduction in incorporation was observed in the presence of excess naphthalene-1-acetic acid. Results from isoelectric focusing gel electrophoresis indicate that the proteins that showed reduced incorporation of photolyzed 5-N3-[7-3H]IAA in the presence of IAA fell into 2 main groups: one which focuses between pH 5.2 and 5.7 (pI 4.8-5.3) and another around pH 6.2 (pI 5.8). In sodium dodecylsulfate polyacrylamide gel electrophoresis, the proteins migrated as 4 bands with apparent MW of 60, 49, 45 and 37 kilodaltons. The auxin-transport inhibitor, 2,3,5-triiodobenzoic acid, competes for the labeling by 5-N3-[7-3H]IAA, suggesting that some of these proteins may be involved in auxin transport.