Search results for "Enzyme Activation"
showing 10 items of 304 documents
Collagen-induced differential expression of an RNA polymerase subunit by breast cancer cells
2005
It was previously reported that the stroma of ductal infiltrating carcinoma (DIC) of the human breast contains considerable amount of an embryo-foetal collagen type, OF/LB (onco-foetal/laminin-binding), and that adhesion of 8701-BC DIC cells onto OF/LB collagen substrates selectively promotes cell growth, motility, production of extracellular lytic enzymes and invasion "in vitro" if compared with other collagen species. To detect possible transcriptional differences for regulatory proteins following OF/LB collagen-cell interactions, we submitted RNA preparations from 8701-BC cells grown on collagen type I, IV and OF/LB to "differential display"-PCR in the presence of degenerate C(2)H(2) zin…
Long-chain fatty acyl-CoA esters induce lipase activation in the absence of a water-lipid interface.
2003
In most lipases a mobile element or lid domain covers the catalytic site of the enzyme and the lid opening event, which usually proceed at a lipid-water interface, is required to form the catalytically competent lipase. We report here a noticeable increase in activity of two fungal lipases assayed in aqueous solution in absence of any interface when adding submicellar concentrations of amphipathic physiological molecules like long-chain acyl-CoAs. The catalytic activity was dramatically dependent on the acyl chain length of the amphiphile and could be related with a lid-opening process. Our data support that lipase activation can be triggered in the absence of a well-defined interface, and …
Hemocyanin conformational changes associated with SDS-induced phenol oxidase activation.
2007
The enzymatic activity of phenoloxidase is assayed routinely in the presence of SDS. Similar assay conditions elicit phenoloxidase activity in another type 3 copper protein, namely hemocyanin, which normally functions as an oxygen carrier. The nature of the conformational changes induced in type 3 copper proteins by the denaturant SDS is unknown. This comparative study demonstrates that arthropod hemocyanins can be converted from being an oxygen carrier to a form which exhibits phenoloxidase activity by incubation with SDS, with accompanying changes in secondary and tertiary structure. Structural characterisation, using various biophysical methods, suggests that the micellar form of SDS is …
Calmodulin binds to p21(Cip1) and is involved in the regulation of its nuclear localization.
1999
p21(Cip1), first described as an inhibitor of cyclin-dependent kinases, has recently been shown to have a function in the formation of cyclin D-Cdk4 complexes and in their nuclear translocation. The dual behavior of p21(Cip1) may be due to its association with other proteins. Different evidence presented here indicate an in vitro and in vivo interaction of p21(Cip1) with calmodulin: 1) purified p21(Cip1) is able to bind to calmodulin-Sepharose in a Ca(2+)-dependent manner, and this binding is inhibited by the calmodulin-binding domain of calmodulin-dependent kinase II; 2) both molecules coimmunoprecipitate when extracted from cellular lysates; and 3) colocalization of calmodulin and p21(Cip…
Activation and translocation of p38 mitogen-activated protein kinase after stimulation of monocytes with contact sensitizers.
2002
Recently we described the induction of tyrosine phosphorylation by contact sensitizers as an early molecular event during the activation of antigen- presenting cells. In this study, the role of the p38 mitogen-activated protein kinase for the activation of human monocytes after exposure to four structurally unrelated contact sensitizers was analyzed in comparison with the irritant benzalkonium chloride and an inductor of oxidative stress (H 2 O 2 ) using immunofluorescence, Western blotting, and enzyme-linked immunosorbent assay techniques. Bio chemical analysis revealed a translocation of p38 from the cytoplasm to the detergent-resistant cell fraction only upon stimulation with contact sen…
Differential salinity-induced variations in the activity of H+-pumps and Na+/H+ antiporters that are involved in cytoplasm ion homeostasis as a funct…
2011
The characterisation of cellular responses to salinity in staple crops is necessary for the reliable identification of physiological markers of salinity tolerance. Under saline conditions, variations in proton gradients that are generated by membrane-bound H⁺ pumps are crucial for maintaining cytoplasm homeostasis. We examined short (15 h) and longer term effects (4 days) of NaCl stress on the H⁺ pumping activities that are associated with the plasma membrane (P-ATPase) and the tonoplast (V-ATPase and V-PPase) in rice (Oryza sativa L.) callus lines that displayed different levels of NaCl tolerance and were established from two japonica rice cultivars. The applied stress conditions were base…
A novel regulatory mechanism of MAP kinases activation and nuclear translocation mediated by PKA and the PTP-SL tyrosine phosphatase
1999
Protein tyrosine phosphatase PTP-SL retains mitogen-activated protein (MAP) kinases in the cytoplasm in an inactive form by association through a kinase interaction motif (KIM) and tyrosine dephosphorylation. The related tyrosine phosphatases PTP-SL and STEP were phosphorylated by the cAMP-dependent protein kinase A (PKA). The PKA phosphorylation site on PTP-SL was identified as the Ser231 residue, located within the KIM. Upon phosphorylation of Ser231, PTP-SL binding and tyrosine dephosphorylation of the MAP kinases extracellular signal–regulated kinase (ERK)1/2 and p38α were impaired. Furthermore, treatment of COS-7 cells with PKA activators, or overexpression of the Cα catalytic subunit …
Late activation of stress kinases (SAPK/JNK) by genotoxins requires the DNA repair proteins DNA-PKcs and CSB.
2005
Although genotoxic agents are powerful inducers of stress kinases (SAPK/JNK), the contribution of DNA damage itself to this response is unknown. Therefore, SAPK/JNK activation of cells harboring specific defects in DNA damage-recognition mechanisms was studied. Dual phosphorylation of SAPK/JNK by the genotoxin methyl methanesulfonate (MMS) occurred in two waves. The early response (≤2 h after exposure) was similar in cells knockout for ATM, PARP, p53, and CSB or defective in DNA-PKcscompared with wild-type cells. The late response however (≥4 h), was drastically reduced in DNA-PKcsand Cockayne's syndrome B (CSB)-deficient cells. Similar results were obtained with human cells lacking DNA-PKc…
Ultraviolet light-induced apoptotic death is impaired by the HMG-CoA reductase inhibitor lovastatin.
2003
HMG-CoA reductase inhibitors (i.e., statins) attenuate C-terminal isoprenylation of Rho GTPases, thereby inhibiting UV-C-induced activation of c-Jun-N-terminal kinases/stress-activated protein kinases (JNKs/SAPKs). Inhibition of UV-C-triggered JNK/SAPK activation by lovastatin is due to inhibition of Rac-SEK1/MKK4-mediated phosphorylation of JNKs/SAPKs at Thr183/Tyr185. UV-C-stimulated phosphorylation of p38 kinase (Thr180/Tyr182) is also impaired by lovastatin. Cell killing provoked by UV-C irradiation was significantly inhibited by lovastatin. This was paralleled by a reduced frequency of chromosomal aberrations, accelerated recovery from UV-C-induced transient replication blockage, inhib…
Comparison of DNase, DNA-polymerase and RNA-polymerase activities present in the DNA-bindung proteins of normal human dermis, epidermis, horny layer …
1978
DNA-binding proteins (DBP) of normal human dermis, epidermis, horny layer and psoriatic scales represent a tissue-specific group of mostly nuclear nonhistone proteins. To analyse their function, the different DBP fractions were examined concerning the presence of DNase, DNA-polymerase and RNA-polymerase activities. DBP of normal epidermis and horny layer contain four different DNases. One DNase of both DBP fractions is active only at pH 5.0. Three DNases of epidermal DBP are active at a pH-range from 5.0--8.5, while the corresponding DNases of horny layer-DBP are most active at pH 7.4. Probably these DNases have changed their pH-optimum during keratinisation. DBP of psoriatic scales include…