Virus-like particles as quantitative probes of membrane protein interactions.

We demonstrate that virus-like particles carrying conformationally complex membrane proteins ("lipoparticles") can be used as soluble probes of membrane protein interactions. To demonstrate the utility of this approach, we use lipoparticles to rapidly differentiate the relative kinetics of membrane protein interactions using optical biosensor technology. The technique is applied to diverse membrane proteins, including G protein-coupled receptors, and used to rank the relative kinetics of nearly all the commercially available monoclonal antibodies against chemokine receptor CCR5. These particles serve as versatile probes for screening crude and purified antibody preparations for receptor specificity, epitope reactivity, and relative binding kinetics.