Troponin (Tn), the complex of three subunits (TnC, TnI and TnT), plays a key role in calcium-dependent regulation of striated muscle contraction. In order to elucidate the interactions between the Tn subunits, we have determined the crystal structure of TnC in complex with the N-terminal fragment of TnI (TnI1-47) at 2.3-angstrom resolution. The TnC/TnI1-47 structure implies a mechanism of how Tn regulate the muscle contraction and suggests a unique a-helical regulatory TnI segment, which binds to the N-lobe of TnC in its calcium-bound comformation.
The x-ray structure of the hydrogenase from Desulfovibrio vulgaris Miyazaki F has been solved at 1.8 Å resolution, and refined to a crystallographic R-factor of 0.229. The high resolution crystal structure enabled us to assign the non-protein ligands to Fe atom in the Ni-Fe site, and revealed the presence of a Mg center. From the nature of the electron density map, stereochemical geometry, and atomic parameters of the refined structure, the most probable candidates for the four ligands have been proposed to be diatomic SO, CO, CN molecules and one sulfur atom.
Hematopoietic prostaglandin (PG) D synthase is the key enzyme for production of the D and J series of prostanoids in the immune system and mast cells. We crystallized the recombinant enzyme, and determined the three-dimensional structure of the enzyme complexed 0 with glutathione at 2.3 Å resolution. The enzyme is the first member of the sigma class glutathione S-transferase (GST) from vertebrates and possesses a prominent cleft as the active site which is never seen among other members of the GST family. The unique 3-D architecture of the catalytic cleft leads to the putative substrate binding mode and its catalytic mechanism, responsible for the specific conversion of PGH2 to PGD2.
Some of complex vanadium (IV, V) oxides are categorized into bronze compounds that adopt open-frame structures with foreign metals in their interstitial sites. There can be a variety of open-frame structure types depending on sizes and amounts of foreign metals as well as on vanadium-oxygen compositions. Utilizing hydrothermal methods we have succeeded in synthesizing single crystals of new vanadium bronze compounds with layered structures. Here we describe crystal structures of the selected novel layered compounds of δ-A0.5V2O5, δ-A0.25V2O5·H2O, AxV3O8 (VO) y·nH2O and Cs2V4O11. Each of these compounds exhibits interesting structural features such as interlayer metal distributions, novel layer frameworks and unusual vanadium-oxygen coordinations.
Cristobalite was compressed under various degree of hydrostaticity in this work. It was clarified that, under high pressure, non-hydrostatic stress affects the crystal structure of high pressure polymorph. A new polymorph of SiO2 was formed under quasi-hydrostatic compression of cristobalite. While the crystal structure of this new polymorph is very similar to that of rutile-type, lattice parameters are different from that of stishovite. No systematic study to clarify the effects of non-hydrostatic stress has ever been made. The effect of non-hydrostatic stress on the crystal lattice was discussed in this paper.