Structure of the antitumour enzyme L-methionine gamma-lyase from Pseudomonas putida at 1.8 A resolution

l-Methionine gamma-lyase (EC 4.4.1.11, MGL_Pp) from Pseudomonas putida is a multifunctional enzyme, which belongs to the gamma-family of pyridoxal-5'-phosphate (PLP) dependent enzymes. In this report, we demonstrate that the three-dimensional structure of MGL_Pp has been completely solved by the molecular replacement method to an R-factor of 20.4% at 1.8 A resolution. Detailed information of the overall structure of MGL_Pp supplies a clear picture of the substrate- and PLP-binding pockets. Tyr59 and Arg61 of neighbouring subunits, which are strongly conserved in other gamma-family enzymes, contact the phosphate group of PLP. These residues are important as the main anchor within the active site. Lys240, Asp241 and Arg61 of one partner monomer and Tyr114 and Cys116 of the other partner monomer form a hydrogen-bond network in the MGL active site which is specific for MGLs. It is also suggested that electrostatic interactions at the subunit interface are involved in the stabilization of the structural conformation. The detailed structure will facilitate the development of MGL_Pp as an anticancer drug.     

Helicobacter pylori dampens gut epithelial self-renewal by inhibiting apoptosis, a bacterial strategy to enhance colonization of the stomach

Colonization of the gastric pits in the stomach by Helicobacter pylori (Hp) is a major risk factor for gastritis, gastric ulcers, and cancer. Normally, rapid self-renewal of gut epithelia, which occurs by a balance of progenitor proliferation and pit cell apoptosis, serves as a host defense mechanism to limit bacterial colonization. To investigate how Hp overcomes this host defense, we use the Mongolian gerbil model of Hp infection. Apoptotic loss of pit cells induced by a proapoptotic agent is suppressed by Hp. The ability of Hp to suppress apoptosis contributed to pit hyperplasia and persistent bacterial colonization of the stomach. Infection with WT Hp but not with a mutant in the virulence effector cagA increased levels of the prosurvival factor phospho-ERK and antiapoptotic protein MCL1 in the gastric pits. Thus, CagA activates host cell survival and antiapoptotic pathways to overcome self-renewal of the gastric epithelium and help sustain Hp infection.     

Effect of electrical stimulation of antagonist muscles for voluntary motor drive

Voluntary motor drive is an important central command that descends via the corticospinal tract to initiate muscle contraction. When electrical stimulation (ES) is applied to an antagonist or agonist muscle, it changes the agonist muscle’s representative motor cortex and thus its voluntary motor drive. In this study, we used a reaction time task to compare the effects of weak and strong ES of the antagonist or agonist muscle during the premotor period of a wrist extension. We recorded motor evoked potentials (MEPs) induced by transcranial magnetic stimulation (TMS) that was applied to the extensor carpi radialis (ECR; agonist) and flexor carpi radialis (FCR; antagonist). When stronger ES intensities were applied to the antagonist, the MEP control ratio in the ECR significantly increased during the premotor time. Furthermore, the MEP control ratio with stronger antagonist ES intensity was significantly larger than that in the agonist for the same ES intensity. In the FCR, the MEP control ratio was also significantly greater at the strong ES intensity than at the weak ES intensity. Furthermore, the MEP control ratio in the antagonist with a strong ES intensity was significantly larger than that in the agonist with the same ES intensity. These results suggest that agonist corticomotor excitability might be enhanced by ES of the antagonist, which in turn strongly activates the descending motor system in the preparation of agonist contraction.     

Modeling associative learning with generalization for a case of warning signals

Animals associative learning plays a crucial role in many intraspecific or interspecific interactions, involving an animals use of information on its interacting counterparts. Here, we present a theoretical model that captures the basic features of an animals associative learning, which may involve generalization, for a simplest case of warning signals. Specifically, we derive formulae for the average level of associative memory as functions of a few parameters that reflect the population density of prey, predators efficiency of prey detection, and the properties of predators associative learning, including generalization and memory decay. This average level of associative memory is of central importance in determining preys fitness and, thus, the evolution of warning signals (i.e. aposematism). The derived formula also shows that another species with similar signal enhances the fitness of an aposematic species of concern as long as their signal is similar enough for generalization to occur. The model developed here can be extended to more complicated cases and the basic idea can be applied to modeling other interactions involving associative learning with generalization.     

Regio-selective preparation of vinyl adenosine ester catalyzed by alkaline protease

The transesterification of divinyladipate with adenosine in DMF containing 20% (v/v) DMSO was catalyzed by Streptomyces sp. alkaline protease and esterification occurred exclusively at the 3-position of hydroxyl group of ribofuranose in adenosine to give 3-O-vinyladipoyl adenosine without other products.     

In vivo priming of natural killer T cells by dendritic cells pulsed with hepatoma-derived acid-eluted substances

Many murine tumor cells express not only individual haplotype-matched class I MHC molecules, but also species-specific CD1d molecules. The former class I MHC molecules generally present internally synthesized tumor-derived peptide antigens to highly specific CD8⁺ cytotoxic T lymphocytes (CTLs) in acquired immunity. In contrast, the latter CD1d molecules may present tumor-associated glycolipid antigens to broadly crossreactive natural killer T (NKT) cells, which might correlate with controlling tumor metastasis. Here, we showed that murine hepatoma cell line Hepa1-6-derived acid-eluted substances might contain both D^b class I MHC-restricted antigens and CD1d-restriced substances, which could sensitize not only syngeneic bone marrow-derived DCs (BM-DCs), but also allogeneic BM-DCs expressing haplotype-mismatched class I MHC and species-specific CD1d molecules. To our surprise, intravenous (i.v.) immunization of C57BL/6 mice with the former syngeneic BM-DCs carrying acid-eluted materials primed both CD4^–CD8^– and CD8⁺ NKT cells in the spleen, whereas immunization with the latter allogeneic BM-DCs loaded the tumor-derived substances primed CD4^–CD8^–, but not CD8⁺ NKT cells. The findings shown in the present study will open a new area for cancer immunotherapy using allogeneic DCs and tumor-derived acid-eluted substances.Abbreviations CTLs cytotoxic T lymphocytes - NKT natural killer T - BM-DCs bone marrow-derived dendritic cells - CTM complete T-cell medium - FCS fetal calf serum - MMC mitomycin C - TCRs T cell receptors     

Identification of three clones which commonly interact with the kinase domains of highly homologous two receptor-like kinases, RLK902 and RKL1

We have previously reported the characterization of highly homologous two leucine-rich repeat (LRR)-receptor-like kinase (RLK) genes, RLK902 and RKL1, which showed 75% identity at the amino acid sequence level. To investigate the RLK902 and RKL1 mediated signal transduction pathways, we performed yeast two-hybrid screening using the kinase domains of RLK902 and RKL1 as baits. Three clones, Y-1, 2 and 3, were found to interact commonly with the kinase domain of RLK902 and RKL1 and not to interact with the kinase domain of BRI1, a member of LRR-RLKs. This result suggests that RLK902 and RKL1 may have common biochemical functions, especially in their downstream signal transduction. Furthermore, the detail analysis of their responsiveness to various conditions suggests their involvement in such stress conditions as mechanical wounding, treatment with salicylic acid, and pathogen infection.     

Maturation of fermented rice-koji miso can be monitored by an increase in fatty acid ethyl ester

A mixture of steamed soybean and boiled rice with seeded Aspergillus oryzae was naturally fermented without addition of yeasts or Lactobacilli, and kept matured for 12 months at room temperature. Chemical analysis of this rice-koji miso sample for lipid changes during maturation showed that triacylglycerol was gradually decomposed into free fatty acid, with distinct formation of fatty acid ethyl ester which, six months after the start of fermentation, came to account for 35.0% of total lipid. The ester was constituted primarily with linoleic acid (ca. 50%) and oleic acid (ca. 20%), no appreciable change in this proportion being observed during maturation. Also, the proportion was unique in that this did not reflect the fatty acid composition in a mixture of the two materials. It is possible to monitor the maturation of the rice-koji miso by following up the increase with time in fatty acid ethyl ester.