Sol M. Gruner
Biomolecules Under Pressure
Humans are biased to think of atmospheric pressure as the typical environment for life on Earth. Yet much, if not most of the life on Earth exists under high pressure conditions encountered deep in the oceans and the Earth’s crust. Given this, remarkably little work has been done on the extraordinary effects of pressure on biomolecules. These effects are often large in magnitude and include pressure denaturation of proteins, as well as dramatic changes in protein monomer-multimer association, substrate binding, membrane ion transport, transcription/translation of DNA & RNA, virus infectivity, enzyme kinetics, and conformational states of proteins. The effects occur even though practically all the biomolecules involved are highly incompressible; hence, volume changes and corresponding compressional energies are necessarily small. The challenges are to understand how pressure affects molecular structure to result in large functional effects and to elucidate the relevant physical mechanisms, as these likely have universal validity. X-ray diffraction studies of proteins under pressure will be described. It is seen that the key point is not the magnitude of the structural changes, but rather the differential compressibility of different parts of the structure.