A Chemiluminescence Based Receptor-ligand Binding Assay Using Peptide Ligands with an Acridinium Ester Label

Abstract

Studying the biochemical interaction of ligands with their corresponding receptors requires highly sensitive detection and monitoring of the bound ligand. Classically, radioactively labelled ligands have been widely used as highly sensitive tools for such binding measurements. Disadvantages of radiolabelling include instability of products, high costs and risks of working with radioactivity. Thus, assays using chemiluminescent probes offer convenient, highly sensitive alternatives. Here we suggest acridinium esters as suitable conjugates to label ligands of interest. Chemical oxidation of acridinium esters triggers chemiluminescence, allowing quantitation of this compound down to amol concentrations in standard luminometers. The first report about acridinium esters in immunoassays date back to 1983 (Weeks et al., 1983) and demonstrated the ability to conjugate acridinium to peptides, followed by using such peptides to measure receptor – peptide ligand interactions (Joss and Towbin, 1994). Recently, this binding assay was adapted for studying derivatives of the plant peptide IDA (INFLORESCENCE DEFICIENT IN ABSCISSION) and their interaction with the corresponding receptor HSL2 (HAESA-LIKE 2) was reported (Butenko et al., 2014). Here we describe how this sensitive, nonradioactive binding approach can be used to reveal receptor-ligand binding in plant material.