Conjugation of Indole-3-Acetic Acid to Proteins and Peptides

吲哚-3-乙酸以游离态和结合态存在于植物体内。研究较少的一种结合IAA的形式是一类独特的蛋白质，其中IAA是直接连接到蛋白质结构上的一个修复基团。越来越多的证据表明，蛋白质稳定性的调节对生长素的功能很重要，因此使这些修饰的蛋白质特别受关注。最近从菜豆中克隆了第一个经IAA共价修饰的蛋白质基因，并发现该基因与其他几种植物中存在的蛋白质有关，包括模式植物阿拉比索植物。四条研究路线将进一步描述植物中的这些蛋白质。1)实验将在分子水平上确定菜豆35 kDa蛋白的表达、调控和功能。2)以前集中在菜豆上的研究将从克隆各自的基因开始，扩展到更适合遗传操作的物种的相关蛋白质，如阿拉伯豆科和Medicago。3)IAA蛋白基因的组织和亚细胞水平的分析将使用报告基因和免疫学技术。4)IAA与蛋白质的结合将使用复杂的液-质联用方法进行分析，这将使这类修饰蛋白的快速鉴定成为可能。这些研究应该提供必要的生化、组织和分子信息，以进一步了解这类独特的修饰蛋白质在植物激素调节中的可能作用。

Indole-3-acetic acid is found in plants in both free and conjugated form. One of the less well-studied forms of conjugated IAA are a unique class of proteins where IAA is a prosthetic group attached directly to the protein structure. An increasing body of evidence suggests that regulation of protein stability is important to auxin function, thus making these modified proteins of particular interest. The first gene for a protein covalently modified by IAA was recently cloned from bean and found to be related to proteins present in several other plant species, including the model plant Arabadopsis. Four lines of study will further characterize these proteins in plants. 1) Experiments will define, on the molecular level, the expression, regulation and function of the bean 35 kDa protein. 2) Previous studies which focused on bean will be extended, starting with cloning the respective genes, to related proteins from species more amenable to genetic manipulation, such as Arabadopsis and Medicago.3) IAA-protein gene expression will be analyzed at the tissue and subcellular level using reporter genes and immunological techniques.4) The attachment of IAA to the proteins will be analyzed using complex liquid chromatography mass spectrometry methods that will allow rapid identification of this class of modified proteins. These studies should provide the biochemical, tissue and molecular information necessary to further understand the possible roles of this unique class of modified proteins in relation to phytohormone regulation.