FEBS Journal

Type IV secretion systems (T4SS) are used by bacteria to exchange materials, DNA or proteins, with the external world. Type I strains of Helicobacter pylori code for a special T4SS, called cytotoxin-associated gene pathogenicity island (cag-PAI). This introduction briefly describes a minireview series that reviews the most recent findings on function, organization and structure of the H. pylori cag-PAI secretion system.

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Bacterial type IV secretion systems (T4SS) form syringe-like pilus structures for the injection of virulence factors into host target cells. One prime example is the Helicobacter pylori T4SS which highjacks integrin receptor β1 for delivery of CagA proteins and peptidoglycan. Here we review the various signalling capabilities of the T4SS, CagA and peptidoglycan, and their contribution to pathogenesis during infection.

The Cag type IV secretion system (Cag-T4SS) is employed by the human gastric pathogen Helicobacter pylori for host cell modulation and virulence. Recent advances in understanding the molecular details of this system have shown considerable differences to related secretion systems from other bacteria. This review describes the functional properties of the Cag-T4SS and highlights its unique features.

The Cag-Type four secretion systems (Cag-T4SS) is a macromolecular assembly used by the human pathogen Helicobacter pylori to inject the toxin CagA. We review the progress made during the past decade in our understanding of the structural biology of the T4SSs and use recent protein-protein interaction data to refine a model of the particular H. pylori Cag-T4SS.

Helicobacter pylori cytotoxin-associated gene-pathogenicity island (cagPAI) includes proteins involved at different levels in pilus assembly, stabilization and processing of secreted substrate as well as regulatory particles possibly involved in the control of T4SS apparatus. In this review we summarize what is known about these accessory components, both from the molecular and structural point of view, and about their putative physiological role.

The structural factors underlying substrate selectivity of copper amine oxidases still remain to be discovered. With this in view, we examined the kinetic behaviour of pea seedling amine oxidase with cadaverine and hexylamine as substrates. Relationships between catalytic and structural parameters were demonstrated on the basis of experiments and computations. A new mechanistic model explaining the substrate-dependent kinetics has been proposed.

It has been shown that calix[4]arene tetrakis-methylene-bis-phosphonic acid (C-192) is the potent inhibitor of fibrin polymerization. An HPLC assay, electron microscopy, blood plasma clotting assays testify to blocking of fibrin formation by combining with fibrin polymerization site ‘A’ (Aα17-19). Results demonstrate that C-192 is a specific inhibitor of fibrin polymerization and blood coagulation and a potential platform for antithrombotic agents.

The wild-type, Q116A, Q116N and Q116H GOB-1 metallo-β-lactamases were studied. Each mutant showed a significantly reduced activity compared to that of the WT. WT and Q116H bound two zinc ions while only one zinc ion was present in Q116A and Q116N. These results suggest that Q116 plays a role in the binding of the zinc ion in the QHH site.

Intracellular accumulation of mannitol is correlated with enhanced resistance of the human pathogenic fungus Aspergillus fumigatus against host defense mechanisms. Metabolic roles of mannitol-1-phosphate 5-dehydrogenase (AfM1PDH) and mannitol 2-dehydrogenase (AfM2DH) were analyzed. Under physiological conditions, AfM1PDH primarily functions as a D-fructose 6-phosphate reductase whereas AfM2DH acts in D-mannitol oxidation. Inhibition of AfM1PDH might be a useful target for therapy.

The methanogen Methanosarcina mazei contains a complex branched respiratory chain with various possibilities to metabolize reducing equivalents. In this study, two mutants of the F₄₂₀ dehydrogenase (ΔfpoA-O and ΔfpoF) were constructed and analyzed, indicating that F₄₂₀ dehydrogenase is the key enzyme in F₄₂₀H₂ oxidation in Ms. mazei. Furthermore, soluble FpoF was identified as ferredoxin: F₄₂₀ oxidoreductase.

Aldo-keto reductase 1B1, the primary human prostaglandin (PG) F_2α synthase, catalyzes NADPH-dependent reduction of PGH₂ to PGF_2α and the isomerization of PGH₂ to PGD₂ in the absence of NADP(H). Site-directed mutagenesis and molecular docking simulation of PGH₂ to the crystallographic structure indicated that His110 acts as a base and an acid to generate PGD₂ and PGF_2α, respectively.

Glucose as a source of energy is centrally important to our understanding of life. We investigated cell division-quiescence behaviour of the fission yeast Schizosaccharomyces pombe under a wide range of glucose concentrations. To characterize the observed phenotypes, we employed a quantitative metabolomic approach and identified specific metabolic biomarkers, which increased or decreased at different glucose concentrations.

This is the first identification of natural substrates of the dipeptidyl peptidase activity of fibroblast activation protein-α (FAP). FAP efficiently hydrolysed neuropeptide Y, B-type natriuretic peptide, substance P and peptide YY, slowly hydrolysed glucagon-like peptide-1 and glucose-dependent insulinotropic peptide, but showed negligible or no hydrolysis of chemokines. These data indicate potential roles for FAP in cardiac function and neurobiology.

We investigated the oligomerization properties of three polymorphic repeat variants of the hD_4.xR by immunoblot analysis, co-immunoprecipitation and bioluminescence resonance energy transfer (BRET) studies. We demonstrate that hD_4.xR oligomerization occurs in the endoplasmic reticulum and plays a role in receptor biogenesis. Furthermore the number of repeats is important for the efficiency and affinity to form oligomers.

A new Ib-subgroup of aspartate aminotransferases (AATB3) was identified from Bacillus subtilis. AATB3 had molecular mass of 49.1 kDa and showed maximal activity at pH8.0 and 45 °C. The K_m values for AATB3 were 6.7, 0.3, 8.0 and 0.7 mm for l-aspartate, α-ketoglutarate, l-glutamate and oxaloacetate, respectively. The aspartate-232, lysine-270 and arginine-403 residues of AATB3 play a key role in transamination.

We examined the efficient induction of HTLV-1-specific CD8+ T-cell response by oligomannose-coated liposomes (OMLs) encapsulating the HTLV-1 Tax-epitope (OML/Tax) in vivo and ex vivo. Our results indicated that OML/Tax efficiently induced the HTLV-1-specific CD8+ T-cell response without adjuvant, suggesting that the efficient antigen delivery system can be exploited to develop a therapeutic vaccine model against tumors and infectious diseases.

In this study, functional characterization of a cotton group C mitogen-activated protein kinase (MAPK) gene (GhMPK2) was carried out. The expression of GhMPK2 was induced by signaling molecules and oxidative stress. Overexpression of GhMPK2 significantly elevated the expression of the pathogenesis-related (PR), signaling-related and antioxidative genes, and thereby enhanced the transgenic plants disease resistance and oxidative stress tolerance.