The binding of salivary amylase to Streptococcus gordonii has previously been shown to involve a 20-kDa amylase-binding protein (AbpA). S. gordonii also releases an 82-kDa protein into the supernatant that binds amylase. To study this 82-kDa component, proteins were precipitated from bacterial culture supernatants by the addition of acetone or purified amylase. Precipitated proteins were separated by SDS-PAGE and transferred to a sequencing membrane. The P2 kDa band was then sequenced, yielding a 25 N-terminal amino acid sequence, CGFIFGRQLTADGSTMFGPTEDYP. Primers derived from this sequence were used in an inverse PCR strategy to clone the full-length gene from S. gordonii chromosomal DNA. An open reading frame of 1959 bp was noted that encoded a 652 amino acid protein having a predicted molecular mass of 80 kDa. The first 24 amino acid residues were consistent with a hydrophobic signal peptide, followed by a 25 amino acid N-terminal sequence that shared identity (24 of 25 residues) with the amino acid sequence of purified AbpB. The abpB gene from strains of S. gordonii was interrupted by allelic exchange with a 420-bp fragment of the abpB gene linked to an erythromycin cassette. The 82-kDa protein was not detected in supernatants from these mutants. These abpB mutants retained the ability to bind soluble amylase. Thus, AbpA, but not AbpB, appears sufficient to be the major receptor for amylase binding to the streptococcal surface. The role of AbpB in bacterial colonization remains to be elucidated. 相似文献
Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy(CADASIL)is a rare hereditary cerebrovascular disease caused by a NOTCH3 mutation.However,the underlying cellular and molecular mechanisms remain unidentified.Here,we generated non-integrative induced pluripotent stem cells(iPSCs)from fibroblasts of a CADASIL patient harboring a heterozygous NOTCH3 mutation(c.3226C>T,p.R1076C).Vascular smooth muscle cells(VSMCs)differentiated from CADASIL-specific iPSCs showed gene expression changes associated with disease phenotypes,including activation of the NOTCH and NF-kB signaling pathway,cytoskeleton disorganization,and excessive cell proliferation.In comparison,these abnormalities were not observed in vascular endothelial cells(VECs)derived from the patients iPSCs.Importantly,the abnormal upregulation of NF-kB target genes in CADASIL VSMCs was diminished by a NOTCH pathway inhibitor,providing a potential therapeutic strategy for CADASIL.Overall,using this iPSCbased disease model,our study identified clues for studying the pathogenic mechanisms of CADASIL and developing treatment strategies for this disease. 相似文献
Sphingolipids have emerged as molecules whose metabolism is regulated leading to generation of bioactive products including ceramide, sphingosine, and sphingosine-1-phosphate. The balance between cellular levels of these bioactive products is increasingly recognized to be critical to cell regulation; whereby, ceramide and sphingosine cause apoptosis and growth arrest phenotypes, and sphingosine-1-phosphate mediates proliferative and angiogenic responses. Sphingosine kinase is a key enzyme in modulating the levels of these lipids and is emerging as an important and regulated enzyme. This review is geared at mechanisms of regulation of sphingosine kinase and the coming to light of its role in disease. 相似文献
It is well established that misfolded forms of cellular prion protein (PrP [PrP(C)]) are crucial in the genesis and progression of transmissible spongiform encephalitis, whereas the function of native PrP(C) remains incompletely understood. To determine the physiological role of PrP(C), we examine the neurophysiological properties of hippocampal neurons isolated from PrP-null mice. We show that PrP-null mouse neurons exhibit enhanced and drastically prolonged N-methyl-d-aspartate (NMDA)-evoked currents as a result of a functional upregulation of NMDA receptors (NMDARs) containing NR2D subunits. These effects are phenocopied by RNA interference and are rescued upon the overexpression of exogenous PrP(C). The enhanced NMDAR activity results in an increase in neuronal excitability as well as enhanced glutamate excitotoxicity both in vitro and in vivo. Thus, native PrP(C) mediates an important neuroprotective role by virtue of its ability to inhibit NR2D subunits. 相似文献
A novel Gram-staining positive, aerobic, rod-shaped, non-motile and yellow-pigmented actinobacterium, designated strain WY83T, was isolated from a marine sediment of Indian Ocean. Strain WY83T grew optimally at 30–35 °C, pH 7–8 and with 0–3% (w/v) NaCl. The predominant menaquinones were MK-10, MK-11 and MK-12, and the major fatty acids were C19:1 ω9c/C19:1 ω11c, anteiso-C15:0, C17:0 3OH, and iso-C16:0. The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol and one unidentified glycolipid. The cell-wall peptidoglycan contained lysine as a diamino acid. The DNA G?+?C content was 72.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences and ninety-two bacterial core genes indicated that strain WY83T formed an evolutionary lineage with Chryseoglobus frigidaquae JCM 14730T, Chryseoglobus indicus CTD02-10-2T, Yonghaparkia alkaliphila JCM 15138T, Microcella alkaliphila DSM 18851T and Microcella putealis DSM 19627T within the radiation enclosing members of the family Microbacteriaceae. All pairwise percentage of conserved proteins between strain WY83T and the closely related phylogenetic neighbors were greater than 65%. The average nucleotide identity and in silico DNA–DNA hybridization values were both below the thresholds used for the delineation of a new species. On the basis of the evidence presented, strains WY83T, Y. alkaliphila JCM 15138T, C. frigidaquae JCM 14730T, M. alkaliphila DSM 18851T and M. putealis DSM 19627T should belong to different species of the same genus. Strain WY83T represents a novel species of the genus Microcella, for which the name Microcella flavibacter sp. nov. is proposed. The type strain is WY83T (=?KCTC 39637T?=?MCCC 1A07099T). Furthermore, Chryseoglobus frigidaquae, Chryseoglobus indicus, and Yonghaparkia alkaliphila were reclassified as Microcella frigidaquae comb. nov., Microcella indica nom. nov., and Microcella alkalica nom. nov., respectively.
Genetic recombination contributes to the diversity of human immunodeficiency virus (HIV-1). Productive HIV-1 recombination is, however, dependent on both the number of HIV-1 genomes per infected cell and the genetic relationship between these viral genomes. A detailed analysis of the number of proviruses and their genetic relationship in infected cells isolated from peripheral blood and tissue compartments is therefore important for understanding HIV-1 recombination, genetic diversity and the dynamics of HIV-1 infection. To address these issues, we used a previously developed single-cell sequencing technique to quantify and genetically characterize individual HIV-1 DNA molecules from single cells in lymph node tissue and peripheral blood. Analysis of memory and naïve CD4+ T cells from paired lymph node and peripheral blood samples from five untreated chronically infected patients revealed that the majority of these HIV-1-infected cells (>90%) contain only one copy of HIV-1 DNA, implying a limited potential for productive recombination in virus produced by these cells in these two compartments. Phylogenetic analysis revealed genetic similarity of HIV-1 DNA in memory and naïve CD4+ T-cells from lymph node, peripheral blood and HIV-1 RNA from plasma, implying exchange of virus and/or infected cells between these compartments in untreated chronic infection. 相似文献
Fifteen Trichoderma isolates were tested for their antagonistic ability against Lasiodiplodia theobromae. Trichoderma harzianum exhibited the greatest inhibition in dual culture. Microscopic investigation demonstrated direct parasitism and coiling of T. harzianum and T. viride around hyphae of L. theobromae, causing swollen, deformed, shortened, or rounded cells of the pathogen. Granulation of cytoplasm and disintegration of the hyphal walls of L. theobromae also were noted in dual culture. Trichoderma viride reduced rotting by 29.07 to 65.06% in artificially inoculated banana fruits. Treatment of banana fruits with T. viride 4 h prior to inoculation with L. theobromae provided better protection than simultaneous application or treatment 4 h after inoculation. 相似文献