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251.
Effect of Docosahexaenoic Acid on the Synthesis of Phosphatidylserine in Rat Brain Microsomes and C6 Glioma Cells 总被引:9,自引:2,他引:7
†Martha C. Garcia †Glenn Ward †Yee-Chung Ma †Norman Salem Jr. † Hee-Yong Kim 《Journal of neurochemistry》1998,70(1):24-30
Abstract: Docosahexaenoic acid (22:6n-3) is the major polyunsaturated fatty acid (PUFA) in the CNS and accumulates particularly in phosphatidylserine (PS). We have investigated the effect of the 22:6n-3 compositional status on the synthesis of PS. The fatty acid composition of brain microsomes from offspring of rats artificially reared on an n-3-deficient diet showed a dramatic reduction of 22:6n-3 content (1.7 ± 0.1%) when compared with control animals (15.0 ± 0.2%). The decrease was accompanied by an increase in docosapentaenoic acid (22:5n-6) content, which replaced the 22:6n-3 phospholipids with 22:5n-6 molecular species, as demonstrated using HPLC/electrospray mass spectrometry. The n-3 deficiency did not affect the total amount of polyunsaturated phospholipids in brain microsomes; however, it was associated with a decrease in the total polyunsaturated PS content and with increased levels of 1-stearoyl-2-docosapentanoyl (18:0/22:5n-6) species, particularly in phosphatidylcholine. Incorporation of [3 H]serine into PS in rat brain microsomes from n-3-deficient animals was slightly but significantly less than that of the control animals. Similarly, C6 glioma cells cultured for 24 h in 22:6n-3-supplemented media (10–40 µ M ) showed a significant increase in the synthesis of [3 H]PS when compared with unsupplemented cells. Our data show that neuronal and glial PS synthesis is sensitive to changes in the docosahexaenoate levels of phospholipids and suggest that 22:6n-3 may be a modulator of PS synthesis. 相似文献
252.
Yokota A Takenaka H Oh T Noda Y Segawa S 《Protein science : a publication of the Protein Society》1998,7(8):1717-1727
Two peptide fragments from tuna cytochrome c (cyt c), N-fragment (residues 1-44 containing the heme) and C-fragment (residues 45-103), combine to form a 1:1 fragment complex. This was clearly proved by ion-spray mass spectrometry. It was found from CD and NMR spectra that the structure of the fragment complex formed is similar to that of an intact cyt c, although each isolated fragment itself is unstructured. Binding constants and enthalpies upon the complex formation were directly observed by isothermal titration calorimetry. Thermodynamic parameters (deltaG(o)b, deltaHb, deltaS(o)b, and deltaC(b)p)) associated with the complex formation were determined at various pHs and temperatures. DeltaHb was found to be almost independent of pH values. The change in heat capacity accompanying the complex formation (deltaC(b)p) was directly determined from the temperature dependence of deltaHb. In addition, the change in heat capacity and enthalpy upon tuna cyt c unfolding were determined by differential scanning calorimetry. Thermodynamic parameters for the unfolding/dissociation process of the fragment complex were compared with those for cyt c unfolding at pH 3.9 and 303 K. In a comparison of two unfolding processes, the heat capacity change of each was very close to the other, while both the unfolding enthalpy and entropy of the fragment complex were larger than those of tuna cyt c. These thermodynamic data suggest that the internal interactions between polar groups (hydrogen bonding) and nonpolar groups (van der Waals interactions) are preserved in the fragment complex as well as in the native state of cyt c. 相似文献
253.
254.
Diane F. Matesic Joseph A. Erwin Edna S. Kaneshiro 《The Journal of eukaryotic microbiology》1998,45(1):156-163
ABSTRACT Paramecium tetraurelia contains high concentrations of ethanolamine sphingolipids, especially in its ciliary membrane. Three ethanolamine sphingophospholipids with different long chain bases (dihydrosphingosine, sphingosine and phytosphingosine), and their phosphonyl analogs, were previously identified and characterized. In the present study, radiolabeling experiments on lag- and log-phase cells were performed to investigate the extent of sphingolipid biosynthetic capacities of the ciliate. Long chain bases of sphingolipids are formed by an initial condensation reaction of serine with a fatty-coenzyme A. Thus, radiolabeled palmitic acid, stearic acid and serine were used as precursor compounds in these experiments. The results indicated that (1) sphingolipid precursors were incorporated into every major lipid fraction. (2) ethanolamine sphingophosphonolipids accumulated faster than the ethanolamine sphingophospholipids, (3) in contrast to these sphingolipids, the glycerolipid, phosphatidyethanolamine. accumulated faster than its phosphono analog, and (4) palmitic acid, but not stearic acid, was incorporated into the long chain bases of ethanolamine sphingophospho- and sphingophosphonolipids. consistent with an earlier report demonstrating that these lipids contain only C,g long chain bases. Since P. tetraurelia takes up serine and other water-soluble substrates very slowly, and catabolizes fatty acids rapidly, label is randomized in intact cells. Thus, cell-free protocols provide useful experimental systems for studies of sphingolipid biosynthesis than do intact organisms, when the uptake of precursor substrates are slow. 相似文献
255.
256.
U-richness is a defining feature of plant introns and may function as an intron recognition signal in maize 总被引:15,自引:2,他引:13
Ko Christopher H. Brendel Volker Taylor Rebecca D. Walbot Virginia 《Plant molecular biology》1998,36(4):573-583
Using a large set of plant gene sequences we compared individual introns to their flanking exons. Both Zea mays and Arabidopsis thaliana introns are U-rich but display no apparent bias for A. We identified fifteen 11-mer U-rich motifs as frequent elements of maize introns, and these are virtually absent from exons. By mutagenesis, we show that the single U-rich motif in the Bronze2 intron of maize plays a key role in intron processing in vivo. 相似文献
257.
258.
S. C. Vashishtha A. J. Nazarali J. R. Dimmock 《Cellular and molecular neurobiology》1998,18(4):437-445
1. Apoptosis as the mechanism of cell death induced by a new cytotoxic and anticancer agent (N.C.1213) was investigated by morphological and biochemical criteria in human Jurkat T leukemia cells.2. The effect of N.C.1213 on the survival of Jurkat T, LV-50, H-9, and Molt-3 cells was measured. Jurkat T cells exhibited the highest response, with less than 10% of the cells remaining viable after exposure to 10 M N.C.1213 for a 24 hr period. All other cell cultures were also affected but to a lesser extent.3. With the use of a fluorescence microscope, several morphological features characteristic of apoptosis such as condensed chromatin and apoptotic bodies were indemnified in Jurkat T cells after exposure to N.C.1213 and melphalan. The results indicated that melphalan was more cytotoxic than N.C.1213 as shown by the dye exclusion test. However, N.C.1213 showed a greater apoptotic index than melphalan. The IC50 of N.C.1213 in Jurkat T cells was determined to be 3.5 M
4. A DNA ladder (fragmentation of DNA into multimers of approximately 200 base pairs), which is one characteristic feature of apoptosis, was not detected when Jurkat T cells were exposed to N.C.1213. Hence it is probable that the key morphological events in apoptosis observed in the present experimental conditions precede the internucleosomalcleavage of DNA. 相似文献
259.
Inactivation of the Pseudomonas aeruginosa mutM, mutY , or mutT gene conferred a 2.4-, 17.2-, or 38.1-fold increase in spontaneous mutation frequency, respectively. Importantly, the mutY and mutT strains each displayed a robust H2 O2 -induced mutation frequency. In addition, the mutM, mutY , and mutT mutations severely sensitized P. aeruginosa to killing by H2 O2 , suggesting that these gene products act to repair one or more cytotoxic lesions in P. aeruginosa . Nucleotide sequence analysis of a fragment of the rpoB gene from rifampicin resistant mutM -, mutY -, and, mutT -deficient strains was consistent with this conclusion. These findings are discussed in terms of possible roles for mutM, mutY , and mutT in contributing to survival and mutagenesis of P. aeruginosa colonizing the airways of cystic fibrosis patients. 相似文献
260.
Chrysoula Vasileiou Wenjing Wang Xiaofei Jia Kin Sing Stephen Lee Camille T. Watson James H. Geiger Babak Borhan 《Proteins》2009,77(4):812-822
Cellular Retinoic Acid Binding Protein II (CRABPII) has been reengineered to specifically bind and react with all‐trans‐retinal to form a protonated Schiff base. Each step of this process has been dissected and four residues (Lys132, Tyr134, Arg111, and Glu121) within the CRABPII binding site have been identified as crucial for imine formation and/or protonation. The precise role of each residue has been examined through site directed mutagenesis and crystallographic studies. The crystal structure of the R132K:L121E‐CRABPII (PDB‐3I17) double mutant suggests a direct interaction between engineered Glu121 and the native Arg111, which is critical for both Schiff base formation and protonation. Proteins 2009. © 2009 Wiley‐Liss, Inc. 相似文献