title: Defining binding efficiency and specificity of auxins for SCF(TIR1/AFB)-Aux/IAA co-receptor complex formation.
abstract: Structure-activity profiles for the phytohormone auxin have been collected for over 70 years, and a number of synthetic auxins are used in agriculture. Auxin classification schemes and binding models followed from understanding auxin structures. However, all of the data came from whole plant bioassays, meaning the output was the integral of many different processes. The discovery of Transport Inhibitor-Response 1 (TIR1) and the Auxin F-Box (AFB) proteins as sites of auxin perception and the role of auxin as molecular glue in the assembly of co-receptor complexes has allowed the development of a definitive quantitative structure-activity relationship for TIR1 and AFB5. Factorial analysis of binding activities offered two uncorrelated factors associated with binding efficiency and binding selectivity. The six maximum-likelihood estimators of Efficiency are changes in the overlap matrixes, inferring that Efficiency is related to the volume of the electronic system. Using the subset of compounds that bound strongly, chemometric analyses based on quantum chemical calculations and similarity and self-similarity indices yielded three classes of Specificity that relate to differential binding. Specificity may not be defined by any one specific atom or position and is influenced by coulomb matrixes, suggesting that it is driven by electrostatic forces. These analyses give the first receptor-specific classification of auxins and indicate that AFB5 is the preferred site for a number of auxinic herbicides by allowing interactions with analogues having van der Waals surfaces larger than that of indole-3-acetic acid. The quality factors are also examined in terms of long-standing models for the mechanism of auxin binding.
authors: School of Life Sciences, University of Warwick , Wellesbourne, Warwickshire CV35 9EF, U.K.
authors: Sarah
authors: S
authors: Lee
authors: Shanthy
authors: S
authors: Sundaram
authors: Lynne
authors: L
authors: Armitage
authors: John P
authors: JP
authors: Evans
authors: Tim
authors: T
authors: Hawkes
authors: Stefan
authors: S
authors: Kepinski
authors: Noel
authors: N
authors: Ferro
authors: Richard M
authors: RM
authors: Napier
mesh_terms: D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016367:Baculoviridae / Q000235:genetics; D001665:Binding Sites; D044783:F-Box Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005822:Genetic Vectors; D007210:Indoleacetic Acids / Q000737:chemistry / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D020349:Surface Plasmon Resonance
chemical_list: C516178:AFB5 protein, Arabidopsis; D029681:Arabidopsis Proteins; D044783:F-Box Proteins; D007210:Indoleacetic Acids; D008024:Ligands; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; C501405:TIR1 protein, Arabidopsis