Modeling and Measurements of Weak Transient Protein-Protein Interactions

Protein-protein interactions are central to many important cellular processes; e.g., molecular recognition, signal transduction, and cellular trafficking to name a few. These cellular processes are characterized by the formation of transient protein complexes that exist in dynamic exchange between the individual proteins and their complexes. Protein-protein interactions that stabilize complex formation can be strong (KD < 1 μM) or weak (KD > 1 μM) depending on the functional requirement. We investigate the interactions that lead to transient protein complexes by measuring the osmotic second virial coefficients characterizing weak protein-protein interactions using composition gradient light scattering. The protein-protein interactions in solutions are modeled using Kirkwood and Goldberg theory of multi-component solution. We measure both the self and cross virial coefficients between the proteins leading to complex formation. In this talk, results on the cross interactions between some well characterized globular proteins such as lysozyme, chymotrypsinogen A, ovalbumin, will be presented.