Search results for "wild type"

Detection of behavioral alterations and learning deficits in mice lacking synaptophysin.

2009

The integral membrane protein synaptophysin is one of the most abundant polypeptide components of synaptic vesicles. It is not essential for neurotransmission despite its abundance but is believed to modulate the efficiency of the synaptic vesicle cycle. Detailed behavioral analyses were therefore performed on synaptophysin knockout mice to test whether synaptophysin affects higher brain functions. We find that these animals are more exploratory than their wild type counterparts examining novel objects more closely and intensely in an enriched open field arena. We also detect impairments in learning and memory, most notably reduced object novelty recognition and reduced spatial learning. Th…

Measurement of cerebral ABCC1 transport activity in wild-type and APP/PS1-21 mice with positron emission tomography

2020

Previous data suggest a possible link between multidrug resistance-associated protein 1 (ABCC1) and brain clearance of beta-amyloid (Aβ). We used PET with 6-bromo-7-[11C]methylpurine ([11C]BMP) to measure cerebral ABCC1 transport activity in a beta-amyloidosis mouse model (APP/PS1-21) and in wild-type mice aged 50 and 170 days, without and with pretreatment with the ABCC1 inhibitor MK571. One hundred seventy days-old-animals additionally underwent [11C]PiB PET scans to measure Aβ load. While baseline [11C]BMP PET scans detected no differences in the elimination slope of radioactivity washout from the brain (kelim) between APP/PS1-21 and wild-type mice of both age groups, PET scans after MK…

2019

The Gram-positive soil bacterium Bacillus subtilis relies on the glutamine synthetase and the glutamate synthase for glutamate biosynthesis from ammonium and 2-oxoglutarate. During growth with the carbon source glucose, the LysR-type transcriptional regulator GltC activates the expression of the gltAB glutamate synthase genes. With excess of intracellular glutamate, the gltAB genes are not transcribed because the glutamate-degrading glutamate dehydrogenases (GDHs) inhibit GltC. Previous in vitro studies revealed that 2-oxoglutarate and glutamate stimulate the activator and repressor function, respectively, of GltC. Here, we have isolated GltC variants with enhanced activator or repressor fu…

Identification of a polyketide synthase gene (pksP) of Aspergillus fumigatus involved in conidial pigment biosynthesis and virulence.

1998

Aspergillus fumigatus is an important pathogen of the immunocompromised host causing pneumonia and invasive disseminated disease with high mortality. Previously, we identified a mutant strain (white, W) lacking conidial pigmentation and, in addition, the conidia showed a smooth surface morphology, whereas wild-type (WT) conidia are grey-green and have a typical ornamentation. W conidia appeared to be less protected against killing by the host defence, e.g., were more susceptible to oxidants in vitro and more efficiently damaged by human monocytes in vitro than WT conidia. When compared to the WT, the W mutant strain showed reduced virulence in a murine animal model. Genetic analysis suggest…

Impact of Acute and Chronic Amyloid-β Peptide Exposure on Gut Microbial Commensals in the Mouse

2020

Alzheimer’s disease (AD) is the most common form of dementia. Besides its cognitive phenotype, AD leads to crucial changes in gut microbiome composition in model mice and in patients, but the reported data are still highly inconsistent. Therefore, we investigated chronic effects of AD-characteristic neurotoxic amyloid-β (Aβ) peptides as provided by transgenic overexpression (5xFAD mouse model) and acute effects due to oral application of Aβ on gut microbes. Astonishingly, one-time feeding of wild type mice with Aβ42 provoked immediate changes in gut microbiome composition (β diversity) as compared to controls. Such obvious changes were not observed when comparing 5xFAD mice with wild type l…

Stability of chitin synthetase in cell-free preparations of a wild-type strain and a 'slime' variant of Neurospora crassa.

1991

Chitin synthetase activity in cell-free preparations from a wild-type strain and a 'slime' variant of Neurospora crassa was monitored over many days in samples stored at 0 degrees C. Total activity in whole-cell-free extracts and low-speed supernatants from both organisms was very unstable, losing more than 90% of the initial activity on storage at 0 degrees C for 96 h. Chitin synthetase detection was not masked by chitinase activity present in the preparations. Gel-filtration chromatography of these preparations increased the stability of the activity from the 'slime' variant, whereas removal of particulate structures by high-speed centrifugation stabilized the chitin synthetase activity i…

Identification of residues in the putative 5th helical region of human interleukin-6, important for activation of the IL-6 signal transducer, gp130

1996

AbstractWe have previously shown that L58 in the putative 5th helical region of human interleukin-6 (IL-6) is important for activation of the IL-6 signal transducer gp130 [de Hon et al. (1995) FEBS Lett. 369, 187–191]. To further explore the importance of individual residues in this region for gp130 activation we have now combined Ala substitutions of residues E52, S53, S54, K55, E56, L58 and E60 with other substitutions in IL-6, known to affect gp130 activation (Q160E and T163P). The combination mutant protein with L58A completely lost the capacity to induce the proliferation of XG-1 myeloma cells, and could effectively antagonize wild type IL-6 activity on these cells. Moreover, the data …

Molecular dynamics studies on HIV-1 protease: a comparison of the flap motions between wild type protease and the M46I/G51D double mutant

2007

The emergence of drug-resistant mutants of HIV-1 is a tragic effect associated with conventional long-treatment therapies against acquired immunodeficiency syndrome. These mutations frequently involve the aspartic protease encoded by the virus; knowledge of the molecular mechanisms underlying the conformational changes of HIV-1 protease mutants may be useful in developing more effective and longer lasting treatment regimes. The flap regions of the protease are the target of a particular type of mutations occurring far from the active site. These mutations modify the affinity for both substrate and ligands, thus conferring resistance. In this work, molecular dynamics simulations were perform…

Theoretical site-directed mutagenesis: Asp168Ala mutant of lactate dehydrogenase

2008

Molecular simulations based on the use of hybrid quantum mechanics/molecular mechanics methods are able to provide detailed information about the complex enzymatic reactions and the consequences of specific mutations on the activity of the enzyme. In this work, the reduction of pyruvate to lactate catalysed by wild-type and Asp168Ala mutant lactate dehydrogenase (LDH) has been studied by means of simulations using a very flexible molecular model consisting of the full tetramer of the enzyme, together with the cofactor NADH, the substrate and solvent water molecules. Our results indicate that the Asp168Ala mutation provokes a shift in the p K a value of Glu199 that becomes unprotonated at n…

Lhca5 interaction with plant photosystem I

2006

AbstractIn the outer antenna (LHCI) of higher plant photosystem I (PSI) four abundantly expressed light-harvesting protein of photosystem I (Lhca)-type proteins are organized in two heterodimeric domains (Lhca1/Lhca4 and Lhca2/Lhca3). Our cross-linking studies on PSI-LHCI preparations from wildtype Arabidopsis and pea plants indicate an exclusive interaction of the rarely expressed Lhca5 light-harvesting protein with LHCI in the Lhca2/Lhca3-site. In PSI particles with an altered LHCI composition Lhca5 assembles in the Lhca1/Lhca4 site, partly as a homodimer. This flexibility indicates a binding-competitive model for the LHCI assembly in plants regulated by molecular interactions of the Lhca…