Studying the assembly of multicomponent protein and ribonucleoprotein complexes using surface plasmon resonance

The assembly of large macromolecular complexes is an important aspect of cellular organization and metabolism. Interactions involving such complexes in principle follow the same rules as the interactions between single proteins or other macromolecules and can therefore be investigated using similar approaches. We have developed protocols employing standard surface plasmon resonance technology that allow the investigation of interactions involving complex macromolecular structures. The principal experimental challenges arise from the possibility of parallel reactions where partially assembled or dissociated subcomplexes form a significant proportion of the molecule population and from an increased likelihood of unspecific binding events owing to the larger surface and statistically higher number of charged areas on multisubunit assemblies. Ways to experimentally avoid or, where this is not possible, to control for these complications are discussed.