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61.
Furanoflavonoids from Pongamia pinnata fruits 总被引:2,自引:0,他引:2
Fruits of Pongamia pinnata afforded four new furanoflavonoids, pongapinnol A-D (1-4), and a new coumestan, pongacoumestan (5) along with thirteen known compounds 6-18. Compounds 16 and 17 are isolated for the first time from this plant. The structures of isolated compounds were elucidated on the basis of spectroscopic data interpretation. 相似文献
62.
Computational approach for prediction of domain organization and substrate specificity of modular polyketide synthases 总被引:9,自引:0,他引:9
Modular polyketide synthases (PKSs) are large multi-enzymatic, multi-domain megasynthases, which are involved in the biosynthesis of a class of pharmaceutically important natural products, namely polyketides. These enzymes harbor a set of repetitive active sites termed modules and the domains present in each module dictate the chemical moiety that would add to a growing polyketide chain. This modular logic of biosynthesis has been exploited with reasonable success to produce several novel compounds by genetic manipulation. However, for harnessing their vast potential of combinatorial biosynthesis, it is essential to develop knowledge based in silico approaches for correlating the sequence and domain organization of PKSs to their polyketide products. In this work, we have carried out extensive sequence analysis of experimentally characterized PKS clusters to develop an automated computational protocol for unambiguous identification of various PKS domains in a polypeptide sequence. A structure based approach has been used to identify the putative active site residues of acyltransferase (AT) domains, which control the specificities for various starter and extender units during polyketide biosynthesis. On the basis of the analysis of the active site residues and molecular modelling of substrates in the active site of representative AT domains, we have identified a crucial residue that is likely to play a major role in discriminating between malonate and methylmalonate during selection of extender groups by this domain. Structural modelling has also explained the experimentally observed chiral preference of AT domain in substrate selection. This computational protocol has been used to predict the domain organization and substrate specificity for PKS clusters from various microbial genomes. The results of our analysis as well as the computational tools for prediction of domain organization and substrate specificity have been organized in the form of a searchable computerized database (PKSDB). PKSDB would serve as a valuable tool for identification of polyketide products biosynthesized by uncharacterized PKS clusters. This database can also provide guidelines for rational design of experiments to engineer novel polyketides. 相似文献
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65.
Zhu Y Nam J Humara JM Mysore KS Lee LY Cao H Valentine L Li J Kaiser AD Kopecky AL Hwang HH Bhattacharjee S Rao PK Tzfira T Rajagopal J Yi H Veena Yadav BS Crane YM Lin K Larcher Y Gelvin MJ Knue M Ramos C Zhao X Davis SJ Kim SI Ranjith-Kumar CT Choi YJ Hallan VK Chattopadhyay S Sui X Ziemienowicz A Matthysse AG Citovsky V Hohn B Gelvin SB 《Plant physiology》2003,132(2):494-505
Limited knowledge currently exists regarding the roles of plant genes and proteins in the Agrobacterium tumefaciens-mediated transformation process. To understand the host contribution to transformation, we carried out root-based transformation assays to identify Arabidopsis mutants that are resistant to Agrobacterium transformation (rat mutants). To date, we have identified 126 rat mutants by screening libraries of T-DNA insertion mutants and by using various “reverse genetic” approaches. These mutants disrupt expression of genes of numerous categories, including chromatin structural and remodeling genes, and genes encoding proteins implicated in nuclear targeting, cell wall structure and metabolism, cytoskeleton structure and function, and signal transduction. Here, we present an update on the identification and characterization of these rat mutants. 相似文献
66.
Antimicrobial polypeptides of the human colonic epithelium 总被引:4,自引:0,他引:4
The lumen of the human colon is heavily colonized with microbes, but infections across its epithelial surface are infrequent. To address the hypothesis that antimicrobial polypeptides contribute to the barrier function of colonic epithelial cells, we examined cellular extracts from non-inflamed colonic mucosa using an antimicrobial assay. This approach yielded five polypeptides: three antimicrobials were previously identified as ribosomal polypeptides (L30, S19 and ubiquicidin), and two were members of the histone family (H1.5 and H2B). All exhibited bactericidal activity against Escherichia coli, and with the exception of S19, had been isolated by others based on their potent antimicrobial activity in other cells and tissues. These polypeptides normally reside inside cells and are proposed to contribute to the formation of the functional antimicrobial barrier of the colonic epithelium. 相似文献
67.
In order to evaluate the modulatory effects of manganese, high fat diet fed and alloxan diabetic rats were taken and the changes
in the glucose oxidation, glycerol release and effects of manganese on these parameters were measured from adipose tissue.
An insulin-mimetic effect of manganese was observed in the adipose tissue in the controls and an additive effect of insulin
and manganese on glucose oxidation was seen when Mn2+ was addedin vitro. The flux of glucose through the pentose phosphate pathway and glycolysis was significantly decreased in high fat fed animals.
Although thein vitro addition of Mn2+ was additive with insulin when14CO2 was measured from control animals, it was found neither in young diabetic animals (6–8 weeks old) nor in the old (16 weeks
old). Both insulin and manganese caused an increased oxidation of carbon-1 of glucose and an increase of its incorporation
into14C-lipids in the young control animals; the additive effect of insulin and manganese suggests separate site of action. This
effect was decreased in fat fed animals, diabetic animals and old animals. Manganese alone was found to decrease glycerol
in both the control and diabetic adipose tissue inin vitro incubations. The results of the effects of glucose oxidation, lipogenesis, and glycerol release in adipose tissue of control
and diabetic animals of different ages are presented together with the effect of manganese on adipose tissue from high fat
milk diet fed animals. 相似文献
68.
The genotoxic effect of hookah smoke was investigated on somatic chromosomes of 35 occupationally nonexposed male hookah smokers. These were compared with an equal number of nonsmokers matched with respect to age, sex, drug intake, if any, and socio-economic status. The mitotic index (MI), chromosomal aberrations (CA), sister chromatid exchanges (SCE) and satellite associations (SA) were analysed. All the parameters showed a significant increase (p < 0.01) in the smokers compared with control individuals, viz MI, 3.88-5.41; CA, 0.94-2.22; SCE, 3.59-5.66; and SA, 5.2-8.65. A distinct time and dose effect relationship was observed. Hookah smoke is thus, both clastogenic and genotoxic for human beings. 相似文献
69.
A. Bhattacharya Monika T. Anand Jayshree Paul Nagendra Yadav S. Bhattacharya 《The Journal of eukaryotic microbiology》1998,45(2):28S-33S
Entamoeba histolytica, the protozoan parasite, is the causative agent of amoebiasis. The degree of virulence, as inferred from invasiveness, of potentially pathogenic strains may be regulated by both host and parasite factors that determine the gut environment. One such factor that plays an important role is the bacterial flora in the gut. Previous studies have clearly shown that bacterial flora is an important determinant of virulence in E. histolytica. However, the exact nature of changes induced in E. histolytica in response to bacteria and their role in virulence is not clear. In this study the levels of a number of molecules potentially important in virulence mechanisms were determined in E. histolytica cells grown with and without normal human bacterial flora, using enzyme-linked immunosorbent assay. Significant changes were observed only after the E. histolytica cells had been adapted to grow with bacterial flora for a number of generations, and not in short term culture. 相似文献
70.
The tribe Iphigenieae (Colchicaceace, Liliales) includes two genera, viz. Camptorrhiza and Iphigenia, which are distributed in Africa, India, and Australasia. Iphigeniais represented by 12 species, of which six occur in India while Camptorrhiza comprises one species each in Africa (C. strumosa) and India (C. indica). The genusCamptorrhiza possesses a knee-shaped tuber attached to the corms, filaments with a thick bulge in the middle and styles with single stigma. Iphigenia on the other hand lacks knee-shaped tuber, bears linear filaments and has styles with three stigmas. Camptorrhiza indica possesses ovoid corms, linear filaments and styles with a single stigma. These characters are intermediate between Iphigenia and Camptorrhiza and hence we studied the cytogenetics and phylogenetic placement of this species to ascertain its generic identity. Somatic chromosome count (2n = 22) and karyotypic features of C. indica are very similar to that of Iphigenia species. Molecular phylogenetic studies based on atpB-rbcL, rps16, trnL, and trnL-F regions showed that C. indica is nested within a lineage of Indian Iphigenia species. Thus, C. indica was reduced to a species of Iphigenia, i.e., I. ratnagirica. Camptorrhiza is now a monotypic genus restricted only to southern Africa. A key to the IndianIphigenia species is provided. In addition, a new combination Wurmbea novae-zelandiae is proposed for Iphigenia novae-zelandiae. 相似文献