1,721,017 research outputs found
The glucose-induced polyphosphoinositides turnover in Saccharomyces cerevisiae is not dependent on the CDC25-RAS mediated signal transduction pathway
No full textCatalase A is involved in the response to photooxidative stress in Pseudomonas aeruginosa
No full textBackground: Pseudomonas aeruginosa is the etiological agent of systemic and skin infections that are often difficult to treat. Photodynamic therapy (PDT) and, more recently, phototherapy (PT), are emerging among antimicrobial treatments to be combined with antibiotics. Visible light, either alone or combined with a photo sensitizer (PS), elicits photooxidative stress that induces microbial death. The response of bacteria to phototherapy seems to involve the antioxidant machinery. This study relies on the effects of detoxifying catalase A (KatA) in response to PDT and PT-induced photooxidative stress.Methods: The photo- and photodynamic inactivation experiments have been targeted at P. aeruginosa PAO1 and its isogenic derivative katA(-) mutant. The microorganisms were irradiated by a wide-spectrum halogen-tungsten lamp or light-emitting diodes (LEDs). Two photosensitizers, Tetrakis-(1-methyl-4-pyridyl)-21H, 23porphine, tetra-p-tosylate (TMPyP) porphyrin and Toluidine Blue O (TBO), were applied as part of the photodynamic approach.Results: P. aeruginosa katA(-) mutant was more sensitive than wild-type strain PAO1 to wide-spectrum light and blue LED (464 nm) treatments. The complementation of KatA, in katA(-) mutant, restored the light response of wild-type PAO1. Upon TBO treatment and irradiation by visible light (halogen lamp or LED), the sensitivity of katA(-) mutant was significant higher (p = 0.028 and p = 0.045, respectively) than that of the PAO1 strain.Conclusions: This study provides the first description of KatA in the response to photooxidative stress induced by photo- and photodynamic therapy
Analysis of the Secondary Structure of the Catalytic Domain of Mouse Ras Exchange Factor CDC25Mm
Full text linkThe minimal active domain GEF domain. of the mouse Ras exchange factor CDC25Mm was purified to homogeneity
from recombinant Escherichia coli culture. The 256 amino acids polypeptide shows high activity in vitro and forms a stable
complex with H-ras p21 in absence of guanine nucleotides. Circular dichroism CD. spectra in the far UV region indicate
that this domain is highly structured with a high content of a-helix 42%.. Near UV CD spectra evidenced good signal due
to phenylalanine and tyrosine while a poor contribution was elicited by the three tryptophan residues contained in this
domain. The tryptophan fluorescence signal was scarcely affected by denaturation of the protein or by formation of the
binary complex with H-ras p21, suggesting that the Trp residues, which are well conserved in the GEF domain of several
Ras-exchange factors, were exposed to the surface of the protein and they are not most probably directly involved in the
interaction with Ras proteins. q1998 Elsevier Science B.
Molecular cloning and regulation of the expression of the MET2 gene of Saccharomyces cerevisiae
No full textEffect of blue light at 410 and 455 nm on Pseudomonas aeruginosa biofilm
No full textPseudomonas aeruginosa is an opportunistic pathogen resistant to many antibiotics, able to form biofilm and causes serious nosocomial infections. Among anti-Pseudomonas light-based approaches, the recent antimicrobial Blue Light (aBL) treatment seems very promising. The aim of this study was to evaluate the efficiency of blue light in inhibiting and/or eradicating P. aeruginosa biofilm. Light at 410 nm has been identified as successful in inhibiting biofilm formation not only of the model strain PAO1, but also of CAUTI (catheter-associated urinary tract infection) isolates characterized by their ability to form biofilm. Results of this work on 410 nm light also demonstrated that: i) at the lowest tested radiant exposure (75 J cm−2) prevents matrix formation; ii) higher radiant exposures (225 and 450 J cm−2) light impairs the cellular components of biofilm, adherent and planktonic ones; iii) light eradicates with a good rate young and older biofilms in a light dose dependent manner; iv) it is also efficient in inactivating catalase A, a virulence factor playing an important role in pathogenic mechanisms. Light at 455 nm, even if at a lower extent than 410 nm, showed a certain anti-Pseudomonas activity. Furthermore, light at 410 nm caused detrimental effects on enzyme activity of β-galactosidase and catalase A, and changes on plasmid DNA conformation and ortho-nitrophenyl-β-D-galactopyranoside structure. This study supports the potential of blue light for anti-infective and disinfection applications
Activation of amyloid precursor protein processing by growth factors is dependent on Ras GTPase activity
No full textThe β-amyloid peptide is generated by the proteolysis of the amyloid precursor protein (APP) by the action
of β- and γ-secretase. The mechanisms underlying this process are poorly understood. Using a cell-based
reporter gene assay we analysed the possible signals and pathways that could be involved in APP cleavage.
We used the stable cell line HeLa AG that expresses the human APP695 fused with the yeast transcription
factor Gal4. This fusion protein is normally translocated into the plasma membrane and after APP-Gal4
cleavage, the AICD-Gal4 fragment released can activate the transcription of a luciferase reporter gene.
Through this reporter system, we demonstrated that Ras GTPase, but not Ral and Rap, could promote APPGal4
cleavage. In addition HeLa AG cells stimulated with EGF or PDGF or overexpressing EGFR exhibit
increased APP proteolysis in a Ras-dependent way. This process is also dependent on γ-secretase activity,
being abolished by the γ-secretase inhibitor DAPT
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