Next generation auxins and anti-auxins : principles for binding and design

背景：植物的生长发育受激素的动态调控。激素是可移动的信号分子，它根据环境信号协调生长。生长素是一种激素，几乎涉及植物生命的每个部分，从胚胎到木材。为了让生长素触发反应，它需要一个受体，一种它以一种非常特定和明确的方式结合的蛋白质。生长素结合就像一个分子开关，启动一系列事件，导致植物的整个基因群被打开或关闭，从而改变发育决定。我们一直在研究一种叫做TIR1的蛋白质作为生长素受体，以及它的家族成员AFB蛋白质。我们已经证明，一些生长素（有很多）对一个或其他受体家族成员具有选择性。目的和目标：本建议描述了一组实验，使我们能够指定和量化家庭成员之间的变化。反过来，这使我们能够描述每种类型的生长素的特殊特征，这些特征决定了特异性，并使我们开始理解定义这种特异性的分子规则。生长素也是有价值的农用化学品。在它们作为除草剂的主要应用中，它们已经表现出一定的选择性，杀死阔叶杂草比杀死谷物要好。然而，我们现在知道有更多层次的选择性可以利用。这使得如果我们要设计新一代的选择性植物生长调节剂，我们必须了解更多关于特异性规则的细节。我们的项目设置了一些互补的实验线，以非常详细地调查区分AFB5的特征，例如，从TIR1。我们将使用最新的生物物理技术来测量结合的速度和结合时的能量变化。通过比较这些值，并将它们与生长素分子本身的计算机驱动计算进行比较，我们将能够推导出每个模板的特定设计特征。此外，我们知道，当生长素与其受体结合时，这种相互作用会为第二种蛋白质，即共同受体创造一个结合位点。我们认为，在结合过程中，TIR1受体作为一种酶来修饰共受体的形状。我们将研究这一假设，并将第二部分共受体组装的动力学细节添加到我们的分子模型中。随着两个初级阶段的完成，我们将有一个详细的信息矩阵，关于是什么使一个分子成为生长素，以及它们是如何选择性的，我们将把它作为设计新的生长素和抗生长素的平台。这些将由同事制作，并测试其功效和选择性。潜在的应用和益处：生长素在农业上的应用包括对花、水果和坚果的处理，以及作为选择性除草剂杀死阔叶植物，而不是谷物和草，具有很大的农业价值。到目前为止，数以百万计的化合物已经被制造和筛选，以找到我们使用的化学物质。该项目将详细测量生长素在其几个但特定的目标位点上产生的非常特殊的相互作用。根据这些信息，我们将开始定义新的和更具选择性的生长素农药的规则，因为到目前为止，农业只开发了生长素类似物。我们的技术将使我们能够将选择性生长素拮抗剂（抗生长素）添加到工具包中。其目的是创造新一代安全、选择性和低剂量的农业化合物。

Context: Plant growth and development are dynamically controlled by hormones. Hormones are mobile signalling molecules which coordinate growth in response to environmental cues. Auxin is a hormone and is involved in almost every part of a plant's life, from embryo to wood. In order for auxin to trigger responses it needs a receptor, a protein to which it binds in a very specific and defined way. Auxin binding acts as a molecular switch, initiating a chain of events that leads to changes in which whole groupings of the plant's genes are switched on or off to change developmental decisions. We have been studying a protein called TIR1 as an auxin receptor, along with members of its family called AFB proteins. We have shown that some auxins (there are many) are selective for one or other receptor family member.Aims and objectives: This proposal describes a set of experiments that allows us to specify and quantify the changes between family members. In turn, this allows us to describe the special features on each type of auxin which determine specificity and allows us to start to understand the molecular rules defining this specificity. Auxins are also valuable agrochemicals. In their main application as herbicides they already present a certain element of selectivity, killing broad-leaved weeds in preference to cereals. However, we now know that there are more layers of selectivity to be exploited. This makes it imperative that we learn much more detail about the rules of specificity if we are to design a new generation of selective plant growth regulators. Our project sets out a number of complimentary lines of experimentation to investigate in great detail the features which differentiate AFB5, for example, from TIR1. We will use the latest biophysical techniques to measure the speeds of binding and the energy changes on binding. By comparing these values and comparing them with computer-driven calculations of the auxin molecules themselves, we will be able to derive design features specific for each template. Further, we know that when auxin binds to its receptor, this interaction creates a binding site for a second protein, a co-receptor. We believe that the TIR1 receptor acts as an enzyme to modify the shape of the co-receptor during binding. We will investigate this hypothesis and add kinetic details of this second part of the co-receptor assembly into our molecular models. With the two primary stages completed, we will have a matrix of detailed information about what makes a molecule an auxin and how they are selective and we will use this as a platform for designing new auxins and anti-auxins. These will be made by colleagues and tested for efficacy and selectivity. Potential applications and benefits: Examples of agricultural use of auxins include treatments to flowers, fruits and nuts and as selective weedkillers to kill broadleaved plants, not cereals and grasses and are of great agricultural value. Up to now, millions of compounds have been made and screened to find the chemicals we use. This project will measure in fine detail the very special interactions made by auxins at their several, but specific target sites. From this information we will start to define rules for new and more selective auxinic agrochemicals because, so far, agriculture has exploited only auxin analogues. Our technologies will enable us to add selective auxin antagonists (anti-auxins) into the toolkit. The aim is to create a new generation of safe, selective and low dosage agricultural compounds.