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101.
Bellincampi D Camardella L Delcour JA Desseaux V D'Ovidio R Durand A Elliot G Gebruers K Giovane A Juge N Sørensen JF Svensson B Vairo D 《Biochimica et biophysica acta》2004,1696(2):265-274
Carbohydrate-active enzymes including glycosidases, transglycosidases, glycosyltransferases, polysaccharide lyases and carbohydrate esterases are responsible for the enzymatic processing of carbohydrates in plants. A number of carbohydrate-active enzymes are produced by microbial pathogens and insects responsible of severe crop losses. Plants have evolved proteinaceous inhibitors to modulate the activity of several of these enzymes. The continuing discovery of new inhibitors indicates that this research area is still unexplored and may lead to new exciting developments. To date, the role of the inhibitors is not completely understood. Here we review recent results obtained on the best characterised inhibitors, pointing to their possible biological role in vivo. Results recently obtained with plant transformation technology indicate that this class of inhibitors has potential biotechnological applications. 相似文献
102.
Design and characterization of helical peptides that inhibit the E6 protein of papillomavirus 总被引:2,自引:0,他引:2
The E6 protein from HPV type 16 binds proteins containing a seven-residue leucine-containing motif. Previous work demonstrated that peptides containing the consensus sequence are a mixture of alpha-helix and unstructured conformations. To design monomeric E6-binding peptides that are stable in aqueous solution, we used a protein grafting approach where the critical residues of the E6-binding motif of E6-associated protein, E6AP, LQELLGE, were incorporated into exposed helices of two stably folded peptide scaffolds. One series was built using the third zinc finger of the Sp1 protein, which contains a C-terminal helix. A second series was built using a Trp-cage scaffold, which contains an N-terminal helix. The chimeric peptides had very different activities in out-competing the E6-E6AP interaction. We characterized the peptides by circular dichroism spectroscopy and determined high-resolution structures by NMR methods. The E6-binding consensus motif was found to be helical in the high-quality structures, which had backbone root-mean-square deviations of less than 0.4 A. We have successfully grafted the E6-binding motif into two parent peptides to create ligands that have biological activity while preserving the stable, native fold of their scaffolds. The data also indicate that conformational change is common in E6-binding proteins during the formation of the complex with the viral E6 protein. 相似文献
103.
The genome sequence of Mycoplasma hyopneumoniae strain 232, the agent of swine mycoplasmosis 总被引:11,自引:0,他引:11 下载免费PDF全文
Minion FC Lefkowitz EJ Madsen ML Cleary BJ Swartzell SM Mahairas GG 《Journal of bacteriology》2004,186(21):7123-7133
We present the complete genome sequence of Mycoplasma hyopneumoniae, an important member of the porcine respiratory disease complex. The genome is composed of 892,758 bp and has an average G+C content of 28.6 mol%. There are 692 predicted protein coding sequences, the average protein size is 388 amino acids, and the mean coding density is 91%. Functions have been assigned to 304 (44%) of the predicted protein coding sequences, while 261 (38%) of the proteins are conserved hypothetical proteins and 127 (18%) are unique hypothetical proteins. There is a single 16S-23S rRNA operon, and there are 30 tRNA coding sequences. The cilium adhesin gene has six paralogs in the genome, only one of which contains the cilium binding site. The companion gene, P102, also has six paralogs. Gene families constitute 26.3% of the total coding sequences, and the largest family is the 34-member ABC transporter family. Protein secretion occurs through a truncated pathway consisting of SecA, SecY, SecD, PrsA, DnaK, Tig, and LepA. Some highly conserved eubacterial proteins, such as GroEL and GroES, are notably absent. The DnaK-DnaJ-GrpR complex is intact, providing the only control over protein folding. There are several proteases that might serve as virulence factors, and there are 53 coding sequences with prokaryotic lipoprotein lipid attachment sites. Unlike other mycoplasmas, M. hyopneumoniae contains few genes with tandem repeat sequences that could be involved in phase switching or antigenic variation. Thus, it is not clear how M. hyopneumoniae evades the immune response and establishes a chronic infection. 相似文献
104.
Assembly of the MexAB-OprM multidrug efflux system of Pseudomonas aeruginosa: identification and characterization of mutations in mexA compromising MexA multimerization and interaction with MexB 下载免费PDF全文
The membrane fusion protein (MFP) component, MexA, of the MexAB-OprM multidrug efflux system of P. aeruginosa is proposed to link the inner (MexB) and outer (OprM) membrane components of this pump as a probable oligomer. A cross-linking approach confirmed the in vivo interaction of MexA and MexB, while a LexA-based assay for assessing protein-protein interaction similarly confirmed MexA multimerization. Mutations compromising the MexA contribution to antibiotic resistance but yielding wild-type levels of MexA were recovered and shown to map to two distinct regions within the N- and C-terminal halves of the protein. Most of the N-terminal mutations occurred at residues that are highly conserved in the MFP family (P68, G72, L91, A108, L110, and V129), consistent with these playing roles in a common feature of these proteins (e.g., oligomerization). In contrast, the majority of the C-terminal mutations occurred at residues poorly conserved in the MFP family (V264, N270, H279, V286, and G297), with many mapping to a region of MexA that corresponds to a region in the related MFP of Escherichia coli, AcrA, that is implicated in binding to its RND component, AcrB (C. A. Elkins and H. Nikaido, J. Bacteriol. 185:5349-5356, 2003). Given the noted specificity of MFP-RND interaction in this family of pumps, residues unique to MexA may well be important for and define the MexA interaction with its RND component, MexB. Still, all but one of the MexA mutations studied compromised MexA-MexB association, suggesting that native structure and/or proper assembly of the protein may be necessary for this. 相似文献
105.
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107.
Venkata R. Krishnamurthy Ann Dougherty Medha Kamat Xuezheng Song Elliot. L. Chaikof 《Carbohydrate research》2010,345(11):1541-1547
Selectins (L, E, and P) are vascular endothelial molecules that play an important role in the recruitment of leukocytes to inflamed tissue. In this regard, P-Selectin glycoprotein-1 (PSGL-1) has been identified as a ligand for P-Selectin. PSGL-1 binds to P-Selectin through the interaction of core-2 O-glycan expressing sialyl Lewisx oligosaccharide and the three tyrosine sulfate residues. Herein, we report the synthesis of threonine-linked core-2 O-glycan as an amino acid building block for the synthesis of PSGL-1. This building block was further incorporated in the Fmoc-assisted solid-phase peptide synthesis to provide a portion of the PSGL-1 glycopeptide. 相似文献
108.
Bio-artificial tissue constructs consisting of fibroblast cells embedded in a collagenous matrix are valuable in vitro systems in which to study cellular mechanics. Deriving cellular mechanics from the results of experimentation on tissue constructs requires a mathematical relationship that delineates amongst the contributions of the constituents of a tissue construct. A scaling between the average strain in a uniformly stretched tissue and the axial strain in isotropic cells was used in earlier work to study relations between cell mechanics and the overall mechanics of a tissue construct. That work showed that a scaling factor called a "strain factor" provided an accurate representation of the average axial strain in isotropic cells. The present study analyzes such relationships for anisotropic cells. We incorporate Eshelby's (1957; Proceedings of the Royal Society of London A 241, 376; 1959; Proceedings of the Royal Society of London A 252, 561) exact solution for the strain field in isolated ellipsoidal inclusions into the Zahalak (Biophysical journal 79, 2369) constitutive model for tissue constructs. Results showed that, for the case of prolate cells, the strain along the major cell axis is mostly influenced by the remote strain projected along that axis; off-axis cell mechanics plays only a small role in most tissues. The strain factor approximation is shown to be accurate for anisotropic cells to within a few percent for the vast majority of tissues. The results presented in this paper provide an explicit measure of the effects of cellular anisotropy, and a mechanism for calculating the contributions of these effects to overall tissue mechanics when these effects are important. 相似文献
109.
110.
Fed-batch two-phase production of alanine
by a metabolically engineered Escherichia coli 总被引:2,自引:0,他引:2
dl-Alanine was produced from glucose in an Escherichia coli pfl pps poxB ldhA aceEF pTrc99A-alaD strain which lacked pyruvate-formate lyase, phosphoenolpyruvate (PEP) synthase, pyruvate oxidase, lactate dehydogenase, components of the pyruvate dehydogenase complex and over-produced alanine dehydrogenase (ALD). A two-phase process was developed with cell growth under aerobic conditions followed by alanine production under anaerobic conditions. Using the batch mode, cells grew to 5.3 g/l in 9 h with the accumulation of 6–10 g acetate/l, and under subsequent anaerobic conditions achieved 34 g alanine/l in 13 h with a yield of 0.86 g/g glucose. Using the fed-batch mode at μ = 0.15 h−1, only about 1 g acetate/l formed in the 25 h required for the cells to reach 5.6 g/l, and 88 g alanine/l accumulated during the subsequent 23 h. This fed-batch process attained an alanine volumetric productivity of 4 g/lh during the production phase, and a yield that was essentially 1 g/g. 相似文献