Search results for "MUTATION"

In the literature: March 2016

2016

The way clones resistant to anti-EGFR (Epidermal Growth Factor Receptor) inhibition evolve in non-small cell lung cancer is far from being determined. In an international cooperative effort led by investigators at Johns Hopkins Hospital in Baltimore, the origin of acquired resistance mediated by the EGFRT790M mutation has been further elucidated. That mutation, recognised as gatekeeper and present in about 60% of pretreated cases with anti-EGFRs, could occur either from the selection of previously existing EGFR790M cell clones or by the evolution of originally EGFR790M-negative drug-tolerant cells. In a series of elegant experiments, the authors show that these drug-tolerant cells have a di…

Melanoma Clinics and Treatment

2013

Role of the metalloprotease Vvp and the virulence plasmid pR99 of Vibrio vulnificus serovar E in surface colonization and fish virulence.

2007

The virulence for eels of Vibrio vulnificus biotype 2 serovar E (VSE) is conferred by a plasmid that codifies ability to survive in eel serum and cause septicaemia. To find out whether the plasmid and the selected chromosomal gene vvp plays a role in the initial steps of infection, the VSE strain CECT4999, the cured strain CT218 and the Vvp-deficient mutant CT201 (obtained in this work by allelic exchange) were used in colonization and virulence experiments. The eel avirulent biotype 1 (BT1) strain YJ016, whose genome has been sequenced, was used for comparative purposes. The global results demonstrate that the plasmid does not play a significant role in surface colonization because (i) CEC…

Functional citric acid cycle in an arcA mutant of Escherichia coli during growth with nitrate under anoxic conditions

1998

The operation of the citric acid cycle of Escherichia coli during nitrate respiration (anoxic conditions) was studied by measuring end products and enzyme activities. Excretion of products other than CO2, such as acetate or ethanol, was taken as an indication for a non-functional cycle. From glycerol, approximately 0.3 mol acetate was produced; the residual portion was completely oxidized, indicating the presence of a partially active citric acid cycle. In an arcA mutant devoid of the transcriptional regulator ArcA, glycerol was completely oxidized with nitrate as an electron acceptor, demonstrating derepression and function of the complete pathway. Glucose, on the other hand, was excreted …

Rapid adaptation of signaling networks in the fungal pathogen Magnaporthe oryzae

2019

Abstract Background One fundamental question in biology is how the evolution of eukaryotic signaling networks has taken place. “Loss of function” (lof) mutants from components of the high osmolarity glycerol (HOG) signaling pathway in the filamentous fungus Magnaporthe oryzae are viable, but impaired in osmoregulation. Results After long-term cultivation upon high osmolarity, stable individuals with reestablished osmoregulation capacity arise independently from each of the mutants with inactivated HOG pathway. This phenomenon is extremely reproducible and occurs only in osmosensitive mutants related to the HOG pathway – not in other osmosensitive Magnaporthe mutants. The major compatible so…

Characterization of a novel open reading frame, urf a, in the mitochondrial genome of fission yeast: correlation of urf a mutations with a mitochondr…

1991

Between the genes for tRNA(gin) and tRNA(ile) an open reading frame of 227 amino acids has been identified which is unique among known mitochondrial genomes and which has been termed urf a (Lang et al. 1983; Kornrumpf et al. 1984). It uses the "mitochondrial" genetic code, i.e., it contains a TGA codon, whereas all other protein-encoding genes, and all but one intronic open reading frame, use the "standard" genetic code (UGG for tryptophan). A previous paper has demonstrated that "mutator" strains show an increased formation of mitochondrial drug-resistant and respiration-deficient mutants (including deletions). In this paper we show that the mutator activity is correlated with mutations in…

The GlpF residue Trp219 is part of an amino-acid cluster crucial for aquaglyceroporin oligomerization and function

2018

The vestibule loop regions of aquaglyceroporins are involved in accumulation of glycerol inside the channel pore. Even though most loop regions do not show high sequence similarity among aquaglyceroporins, loop E is highly conserved in aquaglyceroporins, but not in members of the homologous aquaporins. Specifically, a tryptophan residue is extremely conserved within this loop. We have investigated the role of this residue (Trp219) that deeply protrudes into the protein and potentially interacts with adjacent loops, using the E. coli aqualgyeroporin GlpF as a model. Replacement of Trp219 affects the activity of GlpF and impairs the stability of the tetrameric protein. Furthermore, we have id…

The yeast osmosensitive mutant fps1Δ transformed by the cauliflower BobTIP1;1 aquaporin withstand a hypo-osmotic shock

2005

AbstractOsmoregulation plays an important role in cellular responses to osmotic stress in plants and in yeast. Aquaporins contribute to osmotic adjustment by facilitating transport of water or solutes across membranes. The tonoplastic water channel BobTIP1;1 (original name BobTIP26-1) genes are upregulated during dessication stress in cauliflower meristematic tissue. To investigate the physiological importance of BobTIP1;1, we expressed it in a Saccharomyces cerevisiae osmosensitive mutant fps1Δ. We showed that the defect in the yeast glycerol plasma membrane transporter is complemented by a plant cDNA encoding the aquaporin BobTIP1;1 which is localized in the vacuolar membrane of the compl…

The role of glycerol transporters in yeast cells in various physiological and stress conditions.

2015

Small and uncharged glycerol is an important molecule for yeast metabolism and osmoadaptation. Using a series of S. cerevisiae BY4741-derived mutants lacking genes encoding a glycerol exporter (Fps1p) and/or importer (Stl1p) and/or the last kinase of the HOG pathway (Hog1p), we studied their phenotypes and various physiological characteristics with the aim of finding new roles for glycerol transporters. Though the triple mutant hog1Δ stl1Δ fps1Δ was viable, it was highly sensitive to various stresses. Our results showed that the function of both Stl1p and Fps1p transporters contributes to the cell ability to survive during the transfer into the state of anhydrobiosis, and that the deletion …

A constitutively active pituitary adenylate cyclase activating polypeptide (PACAP) type I receptor shows enhanced photoaffinity labeling of its highl…

2001

Abstract In the present study, we have analyzed a previously identified constitutively active pituitary adenylate cyclase activating polypeptide (PACAP) type I (PAC1) receptor with a deletion of the single amino acid residue Glu 261 (Y.-J. Cao, G. Gimpl, F. Fahrenholz, A mutation of second intracellular loop of pituitary adenylate cyclase activating polypeptide type I receptor confers constitutive receptor activation, FEBS Lett. 469 (2000)). This glutamic acid residue is highly conserved within the second intracellular loop of class II G protein-coupled receptors and may thus be of importance for many members of this receptor class. To explore the molecular characteristics of this mutant re…