Vaults are among the largest cytoplasmic ribonucleoprotein particles and are found in numerous eukaryotic species. Although roles in multidrug resistance and innate immunity have been suggested, the cellular function remains unclear. We have determined the X-ray structure of rat liver vault at 3.5 Å resolution. A vault particle shell was composed of 78 MVP (Major vault protein) chains with 39-fold dihedral symmetry. The shoulder domain of MVP is structurally similar to SPFH (stomatin/prohibitin/flotillin/HflK/C) domain involved in lipid raft association.
Glutamine : fructose 6-phosphate amidotransferase (GFAT) is a rate-limiting enzyme in the hexoamine biosythetic pathway and plays an important role in type 2 diabetes. We now report the first structures of the isomerase domain of the human GFAT in the presence of cyclic glucose 6-phosphate and linear glucosamine 6-phosphate. The C-terminal tail including the active site displays a rigid conformation, similar to the corresponding Escherichia coli enzyme. The diversity of the CF helix near the active site suggests the helix is a major target for drug design. Our study provides insights into the development of therapeutic drugs for type 2 diabetes.
A high-precision diffractometer has been developed for the structure analysis of a submicrometer-scale single grain of a powder sample at the SPring-8 BL40XU undulator beamline. A stable focused synchrotron radiation beam with the phase zone plate and a low eccentric goniometer are the key techniques for measuring accurate diffraction intensity data of a submicrometer-scale single powder grain. In order to verify the performance of the diffractometer, the diffraction pattern data of several submicrometer-scale BaTiO3 grains, with dimensions of 600×600×300 nm, were measured. By identifying the diffraction data set of one single powder grain, the crystal structure was successfully determined. The features of the high-precision diffractometer and the result of the structure analysis of a submicrometer-scale BaTiO3 single powder grain are described.
Charge density studies of photo-induced phase transition materials have been carried out by means of synchrotron radiation powder diffractometry. We found that the photo-excited HS phase in one of spin crossover complexes was distinctly different from both the ground LS and the thermally induced HS phases in a charge density level. The weak electrostatic interaction derived from the suppressed charge density between Fe and N in the photo-excited state should be an origin of the faster relaxation process than the conventional LIESST phenomenon.
In this account, the construction of metallo-supermolecules that behave like machinery is described. A trinuclear Ag (I)-molecular ball bearing is a ligand exchange-driven molecular device. In this complex, two rotor molecules are connected and coaxially arranged by three Ag (I) ions and they can freely rotate relative to each other though cooperative ligand exchange reactions around Ag (I) ions. Furthermore, for a long-range transmission of rotational motion between two rotors 1.5 nm apart from each other, a helical transmitter that can precisely correlate the motions of two terminal rotors was successfully constructed. The motions of two rotors connected with both sides of the transmitter were proven to strongly correlate with each other through a cascade helix inversion of the central transmitter. The structures of these entities were characterized by solution-phase NMR and mass measurements and by a single-crystal X-ray analysis. Moreover, the motions of these supermolecules in solution were analyzed by variable-temperature 1H NMR spectroscopy.