Search results for "mutation."
showing 10 items of 2808 documents
Characterisation of rpsL, rrs and embB mutations associated with streptomycin and ethambutol resistance in Mycobacterium tuberculosis.
2003
In order to characterise molecular mechanisms of first-line drug resistance in Mycobacterium tuberculosis and to evaluate the use of molecular markers of resistance (gene point mutations), we analysed 66 multi-drug-resistant (MDR) isolates from Latvian tuberculosis patients. They were all resistant to rifampin (RIF), isoniazid (INH) and streptomycin (SM), and 33 were resistant to ethambutol (EMB). Enzymatic digestion by MboII and nucleotide sequencing of the rpsL gene fragment detected a single nucleotide substitution K43R in 40 (61%) of the 66 SM-resistant M. tuberculosis isolates. Of the other 26 SM-resistant isolates, 16 (24%) had mutations at positions 513A--C and 516C--T of the rrs gen…
Photobiology in space: An experiment on Spacelab I
1984
The joint European/US Spacelab Mission I, scheduled for October 1983 for a 9 day lasting Earth-orbiting flight, provides a laboratory system for various disciplines of science, including exobiology. On the pallet, in the experiment ES 029 "Microorganisms and Biomolecules in Space Hard Environment" 316 dry samples of Bacillus subtilis spores will be exposed to space vacuum and/or selected wavelenghs of solar UV radiation. After recovery action spectra of inactivation, mutation induction, reparability and photochemical damage in DNA and protein will be determined. The results will contribute to the understanding of the mechanism of the increased UV sensitivity of bacterial spores in vacuo and…
Concomitant loss of conformation and superantigenic activity of staphylococcal enterotoxin B deletion mutant proteins.
1993
The T-cell-stimulating activity of staphylococcal enterotoxin B (SEB) is an important factor in the pathogenesis of certain staphylococcal diseases. To investigate the immunologically active domains of the SEB molecule, we have produced truncated fragments of recombinant SEB by C-terminal and N-terminal deletions. The fragments were expressed as fusion proteins with protein A, including a cleavage site to remove the protein A part. Mutant proteins were tested for the ability to stimulate human resting T cells and SEB-reactive T-cell clones. Deletion of only 9 amino acids from the C terminus leads to complete loss of T-cell-stimulating activity. Removing further amino acids from the SEB mole…
Pseudomonas corrugata crpCDE is part of the cyclic lipopeptide corpeptin biosynthetic gene cluster and is involved in bacterial virulence in tomato a…
2014
Summary: Pseudomonas corrugataCFBP 5454 produces two kinds of cyclic lipopeptides (CLPs), cormycin A and corpeptins, both of which possess surfactant, antimicrobial and phytotoxic activities. In this study, we identified genes coding for a putative non-ribosomal peptide synthetase and an ABC-type transport system involved in corpeptin production. These genes belong to the same transcriptional unit, designated crpCDE. The genetic organization of this locus is highly similar to other PseudomonasCLP biosynthetic clusters. Matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS) analysis revealed that transporter and synthetase genomic knock-out mutants were u…
A frame shift mutation in a hot spot region of the nuclear autoantigen La (SS-B).
1996
A hot spot region was identified in the exon 7 of the nuclear autoantigen La (SS-B). Two La cDNAs were identified which contained a frame shift mutation in the hot spot region. One La cDNA was isolated from a cDNA library made from peripheral blood lymphocytes of an autoimmune patient with primary Sjogren's Syndrome, the other La cDNA was isolated from a human liver cDNA library. The patient's La cDNA had a deletion and the liver La cDNA had an insert of an (A)-residue at the same position. Inserts of 4, 16 and 24 more or less homogeneous (A)-residues were found at the same site in the three La retropseudogenes. The hot spot region located in one of the major autoepitope regions of the La a…
Analysis of expression of an alternative La (SS-B) cDNA and localization of the encoded N- and C-terminal peptides
1997
AbstractA deletion of an (A)-residue was detected in a cDNA encoding for the nuclear autoantigen La/SS-B. The cDNA was recently isolated from a cDNA library made from peripheral blood lymphocytes of a patient with primary Sjögren's Syndrome. The region, where the deletion occurred, represents a hot spot region in the La gene(s). It leads to a frame shift mutation and a premature stop codon eleven amino acids downstream of the deletion site within one of the protease sensitive regions of the La protein. In spite of the frame shift mutation expression of full length La protein occurred efficiently in E. coli. Full length La protein was also made in SF9 cells infected with recombinant baculovi…
The nuclear autoantigen La/SS-B: Mapping and sequencing of the gene and the three retropseudogenes
1997
One target of autoantibodies in sera of patients with systemic lupus erythematosus or primary Sjogren's syndrome is the nuclear autoantigen La/SS-B. Lambda clones and cosmids were isolated, which contained the sequences of the La gene and the three La pseudogenes. They were used for preparation of a physical map. Finally, the La gene and pseudogenes were sequenced. The pseudogenes were characterized as retropseudogenes. Their evolutionary ages were estimated to be approx. 4, 4.5 and 5 million years. Inserts of 4, 16 and 24 nucleotides, which were mostly A-residues, were found in exon 7 of the respective pseudogene. The oldest pseudogene contained the longest insert, the youngest pseudogene …
The human p53 gene mutated at position 249per se is not sufficient to immortalize human liver cells
1999
A particular point mutation of the tumor suppressor gene p53, namely a G→T transversion at the third base of codon 249, is frequently detected in primary hepatocellular carcinomas from patients living in areas where the levels of dietary exposure to aflatoxin B 1 and the rates of infection with the hepatitis B virus are very high. Very recently, a nontumorigenic liver epithelial cell line (HACL-1) with a finite life-span and expressing a number of hepatocyte-specific markers was established from a human hepatocellular adenoma in our laboratory. To analyze the role of mutated p53 in the immortalization of human liver cells, we transfected HACL-1 cells with an expression vector containing a h…
An AFLP clock for the absolute dating of shallow-time evolutionary history based on the intraspecific divergence of southwestern European alpine plan…
2009
The dating of recent events in the history of organisms needs divergence rates based on molecular fingerprint markers. Here, we used amplified fragment length polymorphisms (AFLPs) of three distantly related alpine plant species co-occurring in the Spanish Sierra Nevada, the Pyrenees and the southwestern Alps/Massif Central to establish divergence rates. Within each of these species (Gentiana alpina, Kernera saxatilis and Silene rupestris), we found that the degree of AFLP divergence (D(N72)) between mountain phylogroups was significantly correlated with their time of divergence (as inferred from palaeoclimatic/palynological data), indicating constant AFLP divergence rates. As these rates d…
The Rate and Molecular Spectrum of Spontaneous Mutations in Arabidopsis thaliana
2010
Evolution in Action Rates of evolution in gene and genome sequences have been estimated, but these estimates are subject to error because many of the steps of evolution over the ages are not directly measurable or are hidden under subsequent changes. Ossowski et al. (p. 92 ) now provide a more accurate measurement of how often spontaneous mutations arise in a nuclear genome. Mutations arising over 30 generations were compared by sequencing DNA from individual Arabidopsis thaliana plants. UV- and deamination-induced mutagenesis appeared to bias the type of mutations found.