CagA delivered from Helicobacter pylori into gastric epithelial cells undergoes tyrosine phosphorylation and induces host cell morphological changes. Here we show that CagA can interact with Grb2 both in vitro and in vivo, which results in the activation of the Ras/MEK/ERK pathway and leads to cell scattering as well as proliferation. Importantly, this ability of CagA is independent from the tyrosine phosphorylation, which occurs within the five repeated EPIYA sequences (PY region) of CagA. However, the PY region appears to be indispensable for the Grb2 binding and induction of the cellular responses. Thus, intracellular CagA via its binding to Grb2 may act as a transducer for stimulating growth factor-like downstream signals which lead to cell morphological changes and proliferation, the causes of H. pylori-induced gastric hyperplasia.

An ambient pressure superconductivity of (BEDT-TTF)2Cu(SCN)2 was observed by d.c. magnetic susceptibility and electrical conductivity measurements. The superconducting critical temperature is the highest (TC=10.4 K) among the organic superconductors so far obtained, even though the anion has a positional disorder in the crystal.

SummaryGenetic and functional studies have indicated that the type IV secretion system (TFSS) of Helicobacter pylori forms a secretion complex in the cell envelope that protrudes towards the outside in order to inject CagA protein into gastric epithelial cells. However, the proposed structural model is based on partial amino acid homology with the components of the Agrobacterium tumefaciens TFSS. Therefore, we undertook the identification of the structural features of the TFSS exposed on the surface of H. pylori and found that filamentous structures present on the bacterial surface are related to the secretion apparatus. Using immunofluorescence microscopy with antibodies directed to tyrosine-phosphorylated CagA (pY-CagA) and Hp0532 (VirB7) in the infection assay, pY-CagA signals were detected just below the host cellattached bacteria, where Hp0532 (VirB7) signals were detected as co-localized, suggesting that the CagA injected into the host cell through the TFSS apparatus is still mostly confined to the areas just below the attached bacteria after being phosphorylated. Furthermore, the filamentous structures on bacterium were found to be associated with Hp0532 (VirB7) or Hp0528 (VirB9), the major components of TFSS, by immunogold electron microscopy. These results strongly suggest that the H. pylori TFSS apparatus is a filamentous macromolecular structure protruding from the bacterial envelope.

the present molecule is too simple to distinguish the out-of-plane oxygen vibration from the rigid body libration of the whole molecule. Concluding remarksIn the present calculations, ordinary spherical scattering factors were used for the carbon and hydrogen atoms, and the effect of bond scattering factor (McWeeny, 1952) and the possibility of the charge transfer as a result of the hydrogen bond (Tsubomura, 1954) were completely neglected. In this respect, the present treatment is still too naive to discuss the distribution of valence electrons. Also, an R value of around 10% is sufficient to determine the atomic positions, but not enough to discuss the effect of bonding. This will be the limit of the ordinary photographic measurement of diffraction intensity.One aim of this paper, however, is to show that even at this level of accuracy the introduction of the aspherical atomic scattering factor can improve the results of structure analyses.In the present study, the changes in bond distances and angles were negligible. However, this result should not be considered to be general. If an atom is not centrosymmetric, the imaginary component in equation (10) will introduce the shift of the positional parameter, as discussed by Dawson (1964a).It can be seen from Table 6, that there still remains a small but systematic discrepancy of the Un component of the oxygen atom. This may be due to the effect of bonding.In order to clarify these points, accurate counter measurements at various temperatures are now being planned.

A new crystalline form of perylene has been found and its crystal structure has been determined by the two-dimensional X-ray diffraction method. The new form is monomeric, while the previously known form has a dimeric structure. The electronic absorption and fluorescence spectra of both forms have been measured ; on the basis of these data, an assignment is proposed for the observed transitions. Although the fluorescence spectrum of the monomer form shows a small shift, that of the dimer form shows a larger shift than would be expected from the absorption spectrum. This is explained as a stabilization of the lowest excited singlet state by a charge-transfer resonance interaction between the molecules in a pair. Because this stabilization increases as the distance between two molecules decreases, it is suggested that the molecules in a pair approach each other after excitation. At the liquid helium temperature the motion of molecules in the crystal will be frozen out, the larger stabilization of the excited level cannot occur, and the green emission which is characteristic of the monomer form is observed from the dimer form. The rate process of the molecular motion at lower temperatures has been analyzed.

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The polarized absorption spectra of crystals of indole derivatives have been measured in order to confirm the presence of two types of electronic transitions, 1Lb and 1La, in the long-wavelength absorption region, and in order to determine the direction of their transition moments. The polarization spectra show that the 1A–1Lb electronic transition forms a sharp absroption band with vibrational structures lying below a broader absorption band of the 1A—1La transition. The transition memont direction of the 1Lb makes an angle of 54° to the long axis of the molecule, while that of the 1La lies at an angle of −38° to the same axis. These results were compared with the results of theoretical calculations of the P–P–P SCF MO–CI method.

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