Advances in protein engineering, such as phage display technology, enable us to design antibodies. The recombinant proteins can be expressed in various bacterial hosts, but the expression of antibodies in E. coli often makes insoluble particles, which is considered to be attributed to the folding process of immunoglobulin-folded structure. In this article, the folding study of immunoglobulin structure is summarized and the refolding procedure for antibody fragments from inclusion bodies is elucidated on the basis of the physicochemical folding study of immunoglobulin structure.
The binding of ligands by proteins is accompanied by rapid structural changes that are essential to function. A recent crystallographic study has revealed the ligation-linked protein motions in an allosteric protein, human hemoglobin, in both allosteric forms (T and R) upon photolysis of bound CO at cryogenic temperatures. The results show how differently the α and β subunits, within each allosteric form, respond to loss of ligand, and where the free ligand lies, establishing that the mechanism of protein control of ligand binding is radically different between the subunits.
Internal water molecules are considered to play a crucial role in the functional processes of ion pump proteins, though little has been known about their structure and function. We have studied hydrogen-bonding alterations of internal water molecules in a light-driven proton pump, bacteriorhodopsin, by means of low-temperature Fourier-transform infrared (FTIR) spectroscopy. Highly accurate measurements enabled us to detect even a single stretching vibration of such water molecules. In addition, analysis of the water molecules hydrating with negative charges led to a proposal of the "hydration switch model" for the primary proton transfer reaction in bacteriorhodopsin.