Osmotic and Hydrostatic Pressure as Tools to Study Molecular Recognition

The question of molecular recognition is a central paradigm of molecular biology, playing central roles in most, if not all, cellular processes. Failed recognition events have been implicated in numerous disease states, ranging from flawed control of gene regulation and cellular proliferation to defects in specific metabolic activities. Historically, questions of molecular recognition have been approached through organic synthesis and through actual structural studies of biomolecular complexes. Fundamental insight into the mechanisms of molecular recognition can be realized through the use of broad interdisciplinary tools and techniques. In particular, the use of recombinant DNA technology in concert with hydrostatic and osmotic pressure methodologies have proven to be ideal for understanding the fundamental mechanisms of recognition. In our presentation, we will focus on recent results from our laboratory that examine three major classes of recognition events in biological systems: 1. Protein-protein recognition: here we seek to define the role of specific surface interactions; electrostatic, hydrogen bonding, and hydrophobic free energies provided through surface complimentarity, which define the specificity and affinity in the formation of complexes between the metalloproteins involved in electron transfer events in cytochrome P-450-dependent oxygenase catalysis and in the assembly of tetrameric hemoglobin. 2. Protein—small molecule recognition: here we seek to ascertain how the same fundamental forces of electrostatics, hydrogen bonding, and the hand-glove fit of a substrate into the active site of an enzyme can give rise to the observed high degree of control of regio- and stereo-specificity in catalysis and in the interfadal interactions of proteins at electrode interfaces. 3. Protein nucleic acid recognition: here again the same fundamental forces control recognition processes, but in this case we will focus on our exciting, recent discovery of a role for solvent water in mediating recognition between protein and nucleic acid components. Representative systems in the binding/ catalytic class of restriction endonucleases and recombinases will be discussed. In all cases, the use of pressure as a variable has provided unique understanding for the molecular details of these processes. Pressure, both hydrostatic and osmotic, has proven to be an enabling experimental technique in understanding the mechanistic origins of molecular recognition events.