The crystal structure of the plant small GTPase OsRac1 reveals its mode of binding to NADPH oxidase

This research was originally published in Journal of Biological Chemistry. Ken-ichi Kosami, Izuru Ohki, Minoru Nagano, Kyoko Furuita, Toshihiko Sugiki, Yoji Kawano, Tsutomu Kawasaki, Toshimichi Fujiwara, Atsushi Nakagawa, Ko Shimamoto and Chojiro Kojima. The crystal structure of the plant small GTPase OsRac1 reveals its mode of binding to NADPH oxidase. Journal of Biological Chemistry. 2014; 289, 28569-28578. © the American Society for Biochemistry and Molecular Biology

Fungal effector SIB1 of Colletotrichum orbiculare has unique structural features and can suppress plant immunity in Nicotiana benthamiana

Fungal plant pathogens secrete virulence-related proteins, called effectors, to establish host infection, however, the details are not fully understood yet. Functional screening of effector candidates using Agrobacterium-mediated transient expression assay in Nicotiana benthamiana identified two virulence-related effectors, named SIB1 and SIB2 (Suppression of Immunity in N. benthamiana), of an anthracnose fungus Colletotrichum orbiculare, which infects both cucurbits and N. benthamiana. The Agrobacterium-mediated transient expression of SIB1 or SIB2 increased the susceptibility of N. benthamiana to C. orbiculare, which suggested these effectors can suppress immune responses in N. benthamiana. The presence of SIB1 and SIB2 homologs was found to be limited to the genus Colletotrichum. SIB1 suppressed both (i) the generation of reactive oxygen species (ROS) triggered by two different pathogen-associated molecular patterns (PAMPs), chitin and flg22, and (ii) the cell death response triggered by the Phytophthora infestans INF1 elicitin in N. benthamiana. We determined the NMR-based structure of SIB1 to obtain its structural insights. The three-dimensional structure of SIB1 comprises five β-strands, each containing three disulfide bonds. The overall conformation was found to be a cylindrical shape, such as the well-known antiparallel β-barrel structure. However, the β-strands were found to display a unique topology, one pair of these β-strands formed a parallel β-sheet. These results suggest that the effector SIB1 present in Colletotrichum fungi has unique structural features and can suppress PAMP-triggered immunity (PTI) in N. benthamiana

Light dark matter in NMSSM and implication on Higgs phenomenology

For the experimental search of neutralino dark matter, it is important to know its allowed mass and scattering cross section with the nucleon. In order to figure out how light a neutralino dark matter can be predicted in low energy supersymmetry, we scan over the parameter space of the NMSSM (next-to-minimal supersymmetric model), assuming all the relevant soft mass parameters to be below TeV scale. We find that in the parameter space allowed by current experiments the neutralino dark matter can be as light as a few GeV and its scattering rate off the nucleon can reach the sensitivity of XENON100 and CoGeNT. As a result, a sizable parameter space is excluded by the current XENON100 and CoGeNT data (the plausible CoGeNT dark matter signal can also be explained). The future 6000 kg-days exposure of XENON100 will further explore (but cannot completely cover) the remained parameter space. Moreover, we find that in such a light dark matter scenario a light CP-even or CP-odd Higgs boson must be present to satisfy the measured dark matter relic density. Consequently, the SM-like Higgs boson $h_{SM}$ may decay predominantly into a pair of light Higgs bosons or a pair of neutralinos so that the conventional decays like $h_{SM} -> \gamma \gamma$ is much suppressed.Comment: Version in PLB (discussions added

A novel splice variant of mouse interleukin-1-receptor-associated kinase-1 (IRAK-1) activates nuclear factor-kappaB (NF-kappaB) and c-Jun N-terminal kinase (JNK).

Interleukin-1 (IL-1)-receptor-associated kinase (IRAK) is an indispensable signalling molecule for host-defence responses initiated by a variety of ligands that bind to members of the Toll/IL-1 receptor family. Here we report a novel splice variant of mouse IRAK-1, IRAK-1-S, which is generated by utilizing a new splicing acceptor site within exon 12. IRAK-1-S cDNA is shorter than the originally reported IRAK-1 (IRAK-1-W) cDNA by 271 nucleotides, and the subsequent frameshift causes a premature termination of translation after 23 amino acids, which are unique to the IRAK-1-S protein. To elucidate the physiological function of IRAK-1-S, we overexpressed it in 293T cells and studied the effects on the IL-1 signalling cascade. As it lacks the C-terminal region of IRAK-1-W that has been reported to contain the TRAF6 (tumour necrosis factor receptor-associated factor 6) binding domain, IRAK-1-S was unable to bind TRAF6 protein, which is a proposed downstream signalling molecule. However, IRAK-1-S overexpressed in 293T cells induced constitutive activation of nuclear factor-kappaB (NF-kappaB) and c-Jun N-terminal kinase (JNK) independent of stimulation by IL-1, as did IRAK-1-W. To clarify the mechanism of NF-kappaB activation by IRAK-1-S in the absence of binding to TRAF6, we demonstrated that IRAK-1-S binds to IRAK-1-W through its death domain; the findings suggested that overexpressed IRAK-1-S may bind endogenous IRAK-1-W and activate TRAF6 through IRAK-1-W. These results also indicate that this novel variant may play roles in the activation of NF-kappaB and JNK by IL-1 and other ligands whose signal transduction is dependent on IRAK-1 under physiological conditions

Studies on ²H NMR and single crystal X-ray diffraction of thermochromic bis (N,N-diethyl-1,2-ethanediamine) nickel (II) complexes with and without structural phase transitions

The thermochromic complex bis(N,N-diethyl-1,2-ethanediamine) ((C2H5)2NC2H4NH2) nickel (II) perchlorate([Ni(dieten) 2](ClO4)2) was studied by single crystal X-ray diffraction and found to form a triclinic lattice with space group P1̄, a = 8.108(1)Å, b = 8.835(1)Å, c = 9.736(1)Å, α = 94.24(1)°, β = 114.28(1)°, γ = 116.49(1)° and Z = 1 being isomorphous with that of [Cu(dieten) 2](ClO4)2 which has been reported to have a thermochromic phase transition. The temperature dependences of 2H NMR spectra in [Ni(dieten-d2)2]X2 (dieten-d2: (C2H5)2NC2H4ND2; X: ClO4, BF4, Br, NO3, I) were observed and quadrupole coupling constants e2Qq and asymmetry parameters η were evaluated. Below room temperature, an almost rigid structure of the ND2 group was derived by analyzing the spectra. For perchlorate and tetrafluoroborate with colour changes at respective phase transition temperatures (Tc), quadrupole parameters were also changed discontinuously at Tc. The analysis of spectra observed above Tc afforded two-site jumps of the N-D bond by angles of 52–55° supporting the ring-puckering model of the five-membered chelate ring. However, iodide having no phase transition showed continuous changes of both e2Qq and η values with increasing temperature up to 450 K. These results which cannot be attributed to the puckering motion were explained by whole complex reorientation. These molecular motions are discussed in connection with the colour change observed in these complexes