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排序方式: 共有108条查询结果,搜索用时 15 毫秒
41.
Bacteriophage lysins as effective antibacterials 总被引:2,自引:0,他引:2
Fischetti VA 《Current opinion in microbiology》2008,11(5):393-400
Lysins are highly evolved enzymes produced by bacteriophage (phage for short) to digest the bacterial cell wall for phage progeny release. In Gram-positive bacteria, small quantities of purified recombinant lysin added externally results in immediate lysis causing log-fold death of the target bacterium. Lysins have been used successfully in a variety of animal models to control pathogenic antibiotic resistant bacteria found on mucosal surfaces and infected tissues. The advantages over antibiotics are their specificity for the pathogen without disturbing the normal flora, the low chance of bacterial resistance to lysins, and their ability to kill colonizing pathogens on mucosal surfaces, a capacity previously unavailable. Thus, lysins may be a much needed anti-infective in an age of mounting antibiotic resistance. 相似文献
42.
Sequence and structural characteristics of the trypsin-resistant T6 surface protein of group A streptococci. 总被引:16,自引:4,他引:12
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The gene for the trypsin-resistant surface T6 protein of Streptococcus pyogenes D471 (M type 6) was cloned and expressed in Escherichia coli. The complete nucleotide sequence of the gene (tee6) and its flanking regions was determined and found to include only one major open reading frame coding for a protein of 537 amino acids (Mr, 57,675). The N terminus of the deduced protein sequence exhibits features of a typical signal sequence, and the C-terminal segment was found to have a high degree of homology with the membrane anchor region of other gram-positive surface proteins, such as streptococcal M protein, wapA protein from Streptococcus mutans and staphylococcal protein A. A hexapeptide having the consensus sequence LPSTGE and located immediately upstream of the C-terminal hydrophobic segment showed the highest degree of conservation at both the protein and DNA levels, with nearly all reported surface proteins from gram-positive cocci. The amino acid composition of the T6 protein revealed 21% serine and threonine residues distributed nearly regularly throughout the molecule, and analysis of the secondary structure predicted a conformation composed of greater than 70% beta-sheet potential interrupted by beta-turns or random coils. Localization experiments in E. coli show very little T6 protein in the periplasmic space. When found here, however, this T6 protein had a molecular mass of 55 kilodaltons, similar to that extracted from the streptococci by nonionic detergent. Most of the T6 protein was found localized in the membrane fraction, where it was composed of a triple band of 60, 58, and 57 kilodaltons. The coexistence of streptococcal surface proteins which are either resistant (T protein) or sensitive (M protein) to proteolytic enzymes may offer a new dimension to the modulation of these antigens under specific biological conditions. 相似文献
43.
Ellis NM Li Y Hildebrand W Fischetti VA Cunningham MW 《Journal of immunology (Baltimore, Md. : 1950)》2005,175(8):5448-5456
Mimicry between streptococcal M protein and cardiac myosin is important in the pathogenesis of rheumatic heart disease. M protein-specific human T cell clones derived from rheumatic carditis were cross-reactive with human cardiac myosin, and laminin, a valve protein. Among the 11 CD4(+) and CD8(+) cross-reactive T cell clones, at least 6 different reactivity patterns were distinguished, suggesting different degrees of cross-reactivity and a very diverse T cell repertoire. The latter was confirmed by a heterogeneous Vbeta gene and CDR3 usage. HLA restriction and Th1 cytokine production in response to rM6 protein were preserved when the T cell clones were stimulated by human cardiac myosin or other alpha-helical proteins, such as tropomyosin and laminin. The cross-reactive human T cell clones proliferated to B2 and B3A, dominant peptide epitopes in the B repeat region of streptococcal M protein. In human cardiac myosin, epitopes were demonstrated in the S2 and light meromyosin regions. In our study, T cell mimicry was defined as recognition of structurally related Ags involved in disease and recognized by the same T cell. Mimicry in our study was related to alpha-helical coiled coil proteins which have a repetitive seven-aa residue periodicity that maintains alpha-helical structure and thus creates a high number of degenerate possibilities for recognition by T cells. The study of human T cell clones from rheumatic heart disease revealed potential sites of T cell mimicry between streptococcal M protein and human cardiac myosin and represents some of the most well-defined T cell mimicry in human autoimmune disease. 相似文献
44.
Loss of phylogenetic information in chorion gene families of Bombyx mori gene conversion 总被引:1,自引:0,他引:1
Regier JC; Weigmann BM; Leclerc RF; Friedlander TP 《Molecular biology and evolution》1994,11(1):72-87
The silkmoth chorion has provided a stimulating model for the study of
evolution and developmental regulation of gene families. Previous attempts
at inferring relationships among chorion sequences have been based on
pairwise comparisons of overall similarity, a potentially problematic
approach. To remedy this, we identified the alignable regions of low
sequence variability and then analyzed this restricted database by
parsimony and neighbor-joining methods. At the deepest level, the chorion
sequence tree is split into two branches, called "alpha" and "beta." Within
each branch, early- and late-expressing genes each constitute monophyletic
groups, while the situation with middle-expressing genes remains uncertain.
The HcB gene family appears to be the most basal beta-branch group, but
this conclusion is qualified because the effect of gene conversion on
branching order is unknown. Previous studies by Eickbush and colleagues
have strongly suggested that ErA, HcA, and HcB families undergo gene
conversion within a gene family, whereas the ErB family does not. The
occurrence of conversion correlates with a particular tree structure;
namely, branch lengths are much greater at the base of the family than at
higher internodes and terminal branches. These observations raise the
possibility that chorion gene families are defined by gene conversion
events (reticulate evolution) rather than by descent with modification
(synapomorphy).
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45.
46.
PlyPH, a bacteriolytic enzyme with a broad pH range of activity and lytic action against Bacillus anthracis
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We have cloned a lytic enzyme, PlyPH, with a specific lytic effect on Bacillus anthracis strains. PlyPH remains active between pH 4 and 10.5, and a single dose rescued a significant percentage of mice infected intraperitoneally with an attenuated B. anthracis strain. We propose PlyPH as a novel therapeutic agent. 相似文献
47.
48.
49.
Routine assays to detect proteinases in biological samples are generally tedious and time-consuming. To expedite the recognition of proteinases, we have developed an assay utilizing the gelatin on the surface of an unprocessed Kodak X-Omat AR film as the proteolytic substrate. A positive reaction is indicated by a clear zone on the film after it has been rinsed with running water. This proteinase assay has been found to be inexpensive, rapid, and simple. Besides its ease of use, this assay has been found to be quantitatively reproducible with a well-defined endpoint. More importantly, this assay method is applicable to a variety of proteolytic enzymes under diverse pH (5-8.5) and salt conditions (up to 5 M NaCl) and has a sensitivity similar to that of azocoll. Since the assay does not require sophisticated equipment, it is useful as a general laboratory procedure. 相似文献
50.
Di Perna M Louizou E Fischetti L Dedoussis GV Stanziale P Michelakakis H Zelante L Pras E Bisceglia L 《Genetic testing》2008,12(3):351-355
Mutations in the SLC3A1 and SLC7A9 genes cause cystinuria (OMIM 220100), an autosomal recessive disorder of amino acid transport and reabsorption in the proximal renal tubule and in the epithelial cells of the gastrointestinal tract. In an attempt to characterize the molecular defect in the SLC3A1 and SLC7A9 genes, we analyzed a cohort of 85 unrelated subjects clinically diagnosed as affected by cystinuria on the basis of stone formation, prevalently of Italian and Greek origin. Analysis of all coding region and exon-intron junctions of the SLC3A1 and SLC7A9 genes by using direct sequencing method allowed us to identify 62 different mutations in 83 out of 85 patients accounting for 90.5% of all affected chromosomes. Twenty-four out of 62 are novel mutations, 9 in SLC3A1 and 15 in SLC7A9. In conclusion, this report expands the spectrum of SLC3A1 and SLC7A9 mutations and confirms the heterogeneity of this disorder. 相似文献