Crystal structure of EHEC intimin: insights into the complementarity between EPEC and EHEC

Enterohaemorrhagic E. coli (EHEC) O157:H7 is a primary food-borne bacterial pathogen capable of causing life-threatening human infections which poses a serious challenge to public health worldwide. Intimin, the bacterial outer-membrane protein, plays a key role in the initiating process of EHEC infection. This activity is dependent upon translocation of the intimin receptor (Tir), the intimin binding partner of the bacteria-encoded host cell surface protein. Intimin has attracted considerable attention due to its potential function as an antibacterial drug target. Here, we report the crystal structure of the Tir-binding domain of intimin (Int188) from E. coli O157:H7 at 2.8 Å resolution, together with a mutant (IntN916Y) at 2.6 Å. We also built the structural model of EHEC intimin-Tir complex and analyzed the key binding residues. It suggested that the binding pattern of intimin and Tir between EHEC and Enteropathogenic E. coli (EPEC) adopt a similar mode and they can complement with each other. Detailed structural comparison indicates that there are four major points of structural variations between EHEC and EPEC intimins: one in Domain I (Ig-like domain), the other three located in Domain II (C-type lectin-like domain). These variations result in different binding affinities. These findings provide structural insight into the binding pattern of intimin to Tir and the molecular mechanism of EHEC O157: H7.     

The Improvement of Spinach Growth by Nano-anatase TiO<Subscript>2</Subscript> Treatment Is Related to Nitrogen Photoreduction

The improvement of spinach growth is proved to relate to N₂ fixation by nano-anatase TiO₂ in this study. The results show that all spinach leaves kept green by nano-anatase TiO₂ treatment and all old leaves of control turned yellow white under culture with N-deficient solution. And the fresh weight, dry weight, and contents of total nitrogen, , chlorophyll, and protein of spinach by nano-anatase TiO₂ treatment presented obvious enhancement compared with control. Whereas the improvements of yield of spinach were not as good as nano-anatase TiO₂ treatment under N-deficient condition, confirming that nano-anatase TiO₂ on exposure to sunlight could chemisorb N₂ directly or reduce N₂ to NH₃ in the spinach leaves, transforming into organic nitrogen and improving the growth of spinach. Bulk TiO₂ effect, however, was not as significant as nano-anatase TiO₂. A possible metabolism of the function of nano-anatase TiO₂ reducing N₂ to NH₃ was discussed.     

Reconstitution and characterization of a nicotinic acid adenine dinucleotide phosphate (NAADP)-sensitive Ca2+ release channel from liver lysosomes of rats

Nicotinic acid adenine dinucleotide phosphate (NAADP) is capable of inducing global Ca2+ increases via a lysosome-associated mechanism, but the mechanism mediating NAADP-induced intracellular Ca2+ release remains unclear. The present study reconstituted and characterized a lysosomal NAADP-sensitive Ca2+ release channel using purified lysosomes from rat liver. Furthermore, the identity of lysosomal NAADP-sensitive Ca2+ release channels was also investigated. It was found that NAADP activates lysosomal Ca2+ release channels at concentrations of 1 nM to 1 microM, but this activating effect of NAADP was significantly reduced when the concentrations used increased to 10 or 100 microM. Either activators or blockers of Ca2+ release channels on the sarcoplasmic reticulum (SR) had no effect on the activity of these NAADP-activated Ca2+ release channels. Interestingly, the activity of this lysosomal NAADP-sensitive Ca2+ release channel increased when the pH in cis solution decreased, but it could not be inhibited by a lysosomal H+-ATPase antagonist, bafilomycin A1. However, the activity of this channel was significantly inhibited by plasma membrane L-type Ca2+ channel blockers such as verapamil, diltiazem, and nifedipine, or the nonselective Ca2+,Na+ channel blocker, amiloride. In addition, blockade of TRP-ML1 (transient receptor potential-mucolipin 1) protein by anti-TRP-ML1 antibody markedly attenuated NAADP-induced activation of these lysosomal Ca2+ channels. These results for the first time provide direct evidence that a NAADP-sensitive Ca2+ release channel is present in the lysosome of native liver cells and that this channel is associated with TRP-ML1, which is different from ER/SR Ca2+ release channels.     

艰难梭菌荚膜多糖单糖组成的气相色谱分析

本文对两株艰难梭菌（ＣｄＡ３１８和ＣｄＣＤＣ２７９）荚膜多糖进一步分析,结果证实纯化的艰难梭菌荚膜多糖为单一均匀的物质;经气相色谱分析表明,其单糖组分主要由Ｄ－葡萄糖、Ｄ－甘露糖和Ｄ－半乳糖组成,不同菌株的荚膜多糖可能有微小差异。     

Decreased TUSC3 Promotes Pancreatic Cancer Proliferation,Invasion and Metastasis

Pancreatic cancer is an aggressive disease with dismal prognosis. It is of paramount importance to understand the underlying etiological mechanisms and identify novel, consistent, and easy-to-apply prognostic factors for precision therapy. TUSC3 (tumor suppressor candidate 3) was identified as a potential tumor suppressor gene and previous study showed TUSC3 is decreased in pancreatic cancer at mRNA level, but its putative tumor suppressor function remains to be verified. In this study, TUSC3 expression was found to be suppressed both at mRNA and protein levels in cell line models as well as in clinical samples; decreased TUSC3 expression was associated with higher pathological TNM staging and poorer outcome. In three pairs of cell lines with different NF-κB activity, TUSC3 expression was found to be reversely correlated with NF-κB activity. TUSC3-silenced pancreatic cancer cell line exhibited enhanced potential of proliferation, migration and invasion. In an orthotopic implanted mice model, TUSC3 silenced cells exhibited more aggressive phenotype with more liver metastasis. In conclusion, the current study shows that decreased immunological TUSC3 staining is a factor prognostic of poor survival in pancreatic cancer patients and decreased TUSC3 promotes pancreatic cancer cell proliferation, invasion and metastasis. The reverse correlation between NF-κB activity and TUSC3 expression may suggest a novel regulation pattern for this molecule.     

Photosynthetic Reduction of Xylose to Xylitol Using Cyanobacteria

Photosynthetic generation of reducing power makes cyanobacteria an attractive host for biochemical reduction compared to cell‐free and heterotrophic systems, which require burning of additional resources for the supply of reducing equivalent. Here, using xylitol synthesis as an example, efficient uptake and reduction of xylose photoautotrophically in Synechococcus elongatus PCC7942 are demonstrated upon introduction of an effective xylose transporter from Escherichia coli (Ec‐XylE) and the NADPH‐dependent xylose reductase from Candida boidinii (Cb‐XR). Simultaneous activation of xylose uptake and matching of cofactor specificity enabled an average xylitol yield of 0.9 g g^?1 xylose and a maximum productivity of about 0.15 g L^?1 day^?1 OD^?1 with increased level of xylose supply. While long‐term cellular maintenance still appears challenging, high‐density conversion of xylose to xylitol using concentrated resting cell further pushes the titer of xylitol formation to 33 g L^?1 in six days with 85% of maximum theoretical yield. While the results show that the unknown dissipation of xylose can be minimized when coupled to a strong reaction outlet, it remains to be the major hurdle hampering the yield despite the reported inability of cyanobacteria to metabolize xylose.     

New anti-MRSA cephalosporins with a basic aminopyridine at the C-7 position

Incorporation of a basic aminopyridine into the C-7 position of 3-(amine-substituted arylthio)-3-norcephalosporins, as in 3, afforded high potency against MRSA and acceptable solubility for intravenous administration.