University of Tsukuba

About: University of Tsukuba is a education organization based out in Tsukuba, Ibaraki, Japan. It is known for research contribution in the topics: Population & Gene. The organization has 36352 authors who have published 79483 publications receiving 1934752 citations. The organization is also known as: Tsukuba daigaku & Tsukuba University.

Molecular mechanics of calcium–myristoyl switches

Abstract: Many eukaryotic cellular and viral proteins have a covalently attached myristoyl group at the amino terminus. One such protein is recoverin, a calcium sensor in retinal rod cells, which controls the lifetime of photoexcited rhodopsin by inhibiting rhodopsin kinase1,2,3,4,5,6. Recoverin has a relative molecular mass of 23,000 (Mr 23K), and contains an amino-terminal myristoyl group (or related acyl group) and four EF hands7. The binding of two Ca2+ ions to recoverin leads to its translocation from the cytosol to the disc membrane8,9. In the Ca2+-free state, the myristoyl group is sequestered in a deep hydrophobic box, where it is clamped by multiple residues contributed by three of the EF hands10. We have used nuclear magnetic resonance to show that Ca2+ induces the unclamping and extrusion of the myristoyl group, enabling it to interact with a lipid bilayer membrane. The transition is also accompanied by a 45-degree rotation of the amino-terminal domain relative to the carboxy-terminal domain, and many hydrophobic residues are exposed. The conservation of the myristoyl binding site and two swivels in recoverin homologues from yeast to humans indicates that calcium–myristoyl switches are ancient devices for controlling calcium-sensitive processes.

Antiferromagnetic Spin Fluctuations and Superconductivity in Two-Dimensional Metals —A Possible Model for High Tc Oxides

Abstract: Spin fluctuations in antiferromagnetic and nearly antiferromagnetic two dimensional (square lattice) itinerant electron systems, as a possible model for high T c superconductors, are investigated by using the self-consistent renormalization theory. The electrical resistivity and the nuclear spin relaxation rate due to the spin fluctuations in the normal state are calculated. The results in the nearly antiferromagnetic regime as applied to high T c oxides seem to explain the experimental results both in their temperature dependence and in their orders of magnitudes. By using the same spin fluctuations we discuss superconductivity due to the spin fluctuation mechanism within a weak coupling theory. The order parameter is shown to have B 1 g or A 2 g symmetry and the critical temperature is evaluated to be of the right order of magnitude.

Loss of function of the IAA-glucose hydrolase gene TGW6 enhances rice grain weight and increases yield

Abstract: Increases in the yield of rice, a staple crop for more than half of the global population, are imperative to support rapid population growth. Grain weight is a major determining factor of yield. Here, we report the cloning and functional analysis of THOUSAND-GRAIN WEIGHT 6 (TGW6), a gene from the Indian landrace rice Kasalath. TGW6 encodes a novel protein with indole-3-acetic acid (IAA)-glucose hydrolase activity. In sink organs, the Nipponbare tgw6 allele affects the timing of the transition from the syncytial to the cellular phase by controlling IAA supply and limiting cell number and grain length. Most notably, loss of function of the Kasalath allele enhances grain weight through pleiotropic effects on source organs and leads to significant yield increases. Our findings suggest that TGW6 may be useful for further improvements in yield characteristics in most cultivars.

Antioxidants Enhance Mammalian Proteasome Expression through the Keap1-Nrf2 Signaling Pathway

Abstract: Proteasomes degrade damaged proteins formed during oxidative stress, thereby promoting cell survival. Neurodegenerative and other age-related disorders are associated with reduced proteasome activity. We show herein that expression of most subunits of 20S and 19S proteasomes, which collectively assemble the 26S proteasome, was enhanced up to threefold in livers of mice following treatment with dithiolethiones, which act as indirect antioxidants. Subunit protein levels and proteasome activity were coordinately increased. No induction was seen in mice where the transcription factor Nrf2 was disrupted. Promoter activity of the PSMB5 subunit of the 20S proteasome increased with either Nrf2 overexpression or treatment with antioxidants in mouse embryonic fibroblasts. Tandem antioxidant response elements in the proximal promoter of PSMB5 that controlled these responses were identified. We propose that induction of the 26S proteasome through the Nrf2 pathway represents an important indirect action of these antioxidants that can contribute to their protective effects against chronic diseases.