FORCES GOVERNING PROTEIN RECOGNITION DYNAMICS

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The aim of this research is to directly measure the inter molecular forces governing the dynamics of protein recognition and associations with other proteins, small molecules, and membrane bound receptors. To this end, we will use a surface forces apparatus to directly measure the molecular forces between uniformly oriented protein monolayers and a second protein or ligand monolayer. We will focus on direct measurements of three main aspects of protein structure that impact protein recognition and function: namely, the l) the protein electrostatic surface potentials, 2) the long- ranged inter molecular forces that guide inter molecular docking and enhance kinetic association rates, and 3) the molecular basis of glycosylation or membrane carbohydrate perturbations to protein recognition of macromolecules of membrane-bound receptors. In the first stage of this work, we will directly measure the electrostatic surface potentials of two distinct surface regions of two rat liver cyt b5 variants, the binding surface of cyt c, and the binding surfaces of the Fab' fragments of two monoclonal antifluorescyl IgG idiotypes. We will compare our results with theoretically determined electrostatic potential fields corresponding to the identical protein surface regions. in the second stage, we will elucidate all constituent non contact inter molecular forces such as electrostatic and van der Waals forces that determine protein-ligand association rates. We will also establish the significance of surface charge polarity in reorienting misaligned reactive pairs. We will determine the effects of both active site and external surface mutations on the long ranged inter molecular recognition forces. In the third stage, we will extend our studies beyond the quaternary protein structure to examine the effects of protein glycosylation and membrane glycolipids on both specific and nonspecific protein interactions. We will determine the molecular effects of avidin glycosylation on interfacial binding. We will also determine the impact of gangliosides on receptor-mediated inter membrane adhesion as a function of the ganglioside identity (GM1 and GT3) and of its surface density. Knowledge of the molecular forces governing protein recognition is essential to our understanding of the fundamental basis of protein function. Quantitative determinations of the forces dictating protein behavior will facilitate the a priori predictions of protein function and behavior as well as the rational engineering of proteins with enhanced or finely tailored activities. Furthermore, such measurements will lead to the refinement of existing theoretical models.