Taking up about a third of cellular proteins, oligomeric proteins may confer several advantages, such as functional control, allosteric regulation, and establishment of higher order complexity (Ali et al., Bioorg Med Chem 2005;13:5013–5020). A number of techniques, including biophysical and fluorescent methods, can be used to detect in vitro/in vivo protein association, and/or provide affinity and stoichiometry determination of the interaction (for example, see Gell et al., Adv Exp Med Biol 2012;747:19–41). Among these different approaches, fluorescence polarization, for instance, not only can measure association constants, but is also high-throughput amenable for potential screening of small molecular modulators of protein stability.
In their article, Gray and co-workers* report an alternative plate based assay to study regulation of protein self-assembly and its effect on protein interactions. An emerging cancer drug target, pro-oncogenic protein anterior gradient-2 (AGR2), was applied as a model protein for this study due to the existence of a previously reported dimeric species. Using a fluorescently conjugated monoclonal antibody (MAB) and a far infrared emission as the readout, the assay design was based on the MAB recognition of separate epitopes that occurred only when AGR2 was in an oligomeric format (see Figure 1).