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171.
172.
Peptide deformylase (PDF) catalyses the removal of the N-formyl group from the nascent polypeptide during protein maturation. The PDF of Mycobacterium tuberculosis H37Rv (MtbPDF), overexpressed and purified from Escherichia coli, was characterized as an iron-containing enzyme with stability towards H(2) O(2) and moderate thermostability. Substitution of two conserved residues (G49 and L107) from MtbPDF with the corresponding residues found in human PDF affected its deformylase activity. Among characterized PDFs, glycine (G151) in motif III instead of conserved aspartate is characteristic of M. tuberculosis. Although the G151D mutation in MtbPDF increased its deformylase activity and thermostability, it also affected enzyme stability towards H(2) O(2) . Molecular dynamics and docking results confirmed improved substrate binding and catalysis for the G151D mutant and the study provides another possible molecular basis for the stability of MtbPDF against oxidizing agents. 相似文献
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174.
Bacterial nitric-oxide synthase proteins (NOSs) from certain Streptomyces strains have been shown to participate in biosynthetic nitration of tryptophanyl moieties in vivo (Kers, J. A., Wach, M. J., Krasnoff, S. B., Cameron, K. D., Widom, J., Bukhaid, R. A., Gibson, D. M., and Crane, B. R., and Loria, R. (2004) Nature 429, 79-82). We report that the complex between Deinococcus radiodurans NOS (deiNOS) and an unusual tryptophanyl-tRNA synthetase (TrpRS II) catalyzes the regioselective nitration of tryptophan (Trp) at the 4-position. Unlike non-enzymatic Trp nitration, and similar reactions catalyzed by globins and peroxidases, deiNOS only produces the otherwise unfavorable 4-nitro-Trp isomer. Although deiNOS alone will catalyze 4-nitro-Trp production, yields are significantly enhanced by TrpRS II and ATP. 4-Nitro-Trp formation exhibits saturation behavior with Trp (but not tyrosine) and is completely inhibited by the addition of the mammalian NOS cofactor (6R)-5,6,7,8-tetrahydro-l-biopterin (H(4)B). Trp stimulates deiNOS oxidation of substrate l-arginine (Arg) to the same degree as H(4)B. These observations are consistent with a mechanism where Trp or a derivative thereof binds in the NOS pterin site, participates in Arg oxidation, and becomes nitrated at the 4-position. 相似文献
175.
Nair MP Mahajan SD Schwartz SA Reynolds J Whitney R Bernstein Z Chawda RP Sykes D Hewitt R Hsiao CB 《Journal of immunology (Baltimore, Md. : 1950)》2005,174(11):6617-6626
We report that cocaine may act as cofactor in HIV pathogenesis by increasing dendritic cell-specific C type ICAM-3-grabbing nonintegrin (DC-SIGN) expression on dendritic cells (DC). Our results show that cocaine-using, long-term nonprogressors and normal progressors of HIV infection manifest significantly higher levels of DC-SIGN compared with cocaine-nonusing long-term nonprogressors and normal progressors, respectively. Furthermore, in vitro HIV infection of MDC from normal subjects cultured with cocaine and/or HIV peptides up-regulated DC-SIGN, confirming our in vivo finding. Cocaine, in synergy with HIV peptides, also up-regulates DC-SIGN gene expression by MDC. Furthermore, the cocaine-induced effects were reversed by a D1 receptor antagonist demonstrating the specificity of the reaction. Our results indicate that cocaine exacerbates HIV infection by up-regulating DC-SIGN on DC and these effects are mediated via dysregulation of MAPKs. These data are the first evidence that cocaine up-regulates the expression of DC-SIGN on DC. A better understanding of the role of DC-SIGN in HIV infection may help to design novel therapeutic strategies against the progression of HIV disease in the drug-using population. 相似文献
176.
The neuromuscular junction (NMJ) is a synapse that develops between a motor neuron and a muscle fiber. A defining feature of NMJ development in vertebrates is the re-distribution of muscle acetylcholine (ACh) receptors (AChRs) following innervation, which generates high-density AChR clusters at the postsynaptic membrane and disperses aneural AChR clusters formed in muscle before innervation. This process in vivo requires MuSK, a muscle-specific receptor tyrosine kinase that triggers AChR re-distribution when activated; rapsyn, a muscle protein that binds and clusters AChRs; agrin, a nerve-secreted heparan-sulfate proteoglycan that activates MuSK; and ACh, a neurotransmitter that stimulates muscle and also disperses aneural AChR clusters. Moreover, in cultured muscle cells, several additional muscle- and nerve-derived molecules induce, mediate or participate in AChR clustering and dispersal. In this review we discuss how regulation of AChR re-distribution by multiple factors ensures aggregation of AChRs exclusively at NMJs. 相似文献
177.
Nimisha R. Nair Vini C. Sekhar K. Madhavan Nampoothiri 《Indian journal of microbiology》2016,56(1):59-63
Bioplastics are eco-friendly and derived from renewable biomass sources. Innovation in recycling methods will tackle some of the critical issues facing the acceptance of bioplastics. Polylactic acid (PLA) is the commonly used and well-studied bioplastic that is presumed to be biodegradable. Considering their demand and use in near future, exploration for microbes capable of bioplastic degradation has high potential. Four PLA degrading strains were isolated and identified as Penicillium chrysogenum, Cladosporium sphaerospermum, Serratia marcescens and Rhodotorula mucilaginosa. A consortium of above strains degraded 44 % (w/w) PLA in 30 days time in laboratory conditions. Subsequently, the microbial consortium employed effectively for PLA composting.
Electronic supplementary material
The online version of this article (doi:10.1007/s12088-015-0559-z) contains supplementary material, which is available to authorized users. 相似文献178.
The clustering of acetylcholine receptors (AChRs) in muscle is a hallmark step in the development of vertebrate neuromuscular junctions (NMJs). It involves localized signaling, which is initiated by the activation of MuSK (muscle-specific kinase) and leads to the concentration and cytoskeletal anchoring of AChRs at the synapse, and global signaling, which traverses the muscle to disperse extra-synaptic AChR clusters. Here we review some of the recent findings that indicate important roles for the actin cytoskeleton and tyrosine phosphatases in mediating these processes. 相似文献
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180.
Panjamurthy K Manoharan S Menon VP Nirmal MR Senthil N 《Journal of biochemical and molecular toxicology》2008,22(4):251-258
The present study has investigated the antigenotoxic effect of withaferin-A, a steroidal lactone obtained from the roots and leaves of Withania somnifera, in 7,12-dimethylbenz(a)anthracene (DMBA)-induced genotoxicity. Measurement of the frequency of micronucleated polychromatic erythrocytes (MnPCEs) and chromosomal aberrations is used as cytogenetic endpoints. A single intraperitoneal injection of DMBA (30 mg/kg b.w.) to golden Syrian hamsters resulted in marked elevation in the frequency of MnPCEs and aberrations in the chromosomal structure. Hamsters pretreated with withaferin-A intraperitonealy 2 h before the injection of DMBA, significantly reduced the frequency of MnPCEs and chromosomal aberrations such as chromosomal break, gap, minute, and fragment. Our results thus demonstrated the antigenotoxic effect of withaferin-A in DMBA-induced genotoxicity in the bone marrow of golden Syrian hamsters. 相似文献