Abstract
High-pressure protein X-ray crystallography (HPPX) is a unique method that provides high-resolution structural information under various pressure conditions including hydration waters at a molecular surface and internal cavities. Two important applications of HPPX are (1) studying the mechanism of pressure tolerance of proteins from several organisms living in deep seas and (2) observation of functional sub-states of biological macromolecules. After brief introduction, two examples of the recent advances are described in this article. The first one is the study on the mechanism of pressure tolerance of 3-isopropylmalate dehydrogenase from high-pressure adapted deep-sea organisms. The second example is the observation of pressure-induced conformational substate of hen egg white lysozyme, which reveals a part of the reaction mechanism of the enzyme.
