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排序方式: 共有262条查询结果,搜索用时 15 毫秒
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Cholesteryl ester transfer protein is secreted by Hep G2 cells and contains asparagine-linked carbohydrate and sialic acid 总被引:2,自引:0,他引:2
T L Swenson J S Simmons C B Hesler C Bisgaier A R Tall 《The Journal of biological chemistry》1987,262(34):16271-16274
A cholesteryl ester transfer protein (CETP) of apparent Mr 74,000 has recently been purified from human plasma. Cholesteryl ester transfer activity was found to accumulate in the medium of cultured Hep G2 cells. The transfer activity was removed by immunoprecipitation with specific antibodies to the plasma CETP. Sodium dodecyl sulfate gel electrophoresis of immunoprecipitates prepared from the medium of cells pulsed with [35S]methionine revealed a broad specific band of protein of Mr 72,000 to 76,000; by contrast, immunoprecipitates of cellular homogenates showed a sharp specific band of Mr 58,000. The Mr 72,000 to 76,000 band disappears, concomitant with the appearance of lower Mr products, upon neuraminidase or glycopeptidase F treatment of medium immunoprecipitates or of purified CETP. The results indicate that liver cells have the capacity to synthesize and secrete CETP. The CETP peptide acquires asparagine-linked carbohydrate and sialic acid during intracellular processing. 相似文献
4.
Recognition of vesicular lipoproteins by the apolipoprotein B,E receptor of cultured fibroblasts 总被引:2,自引:0,他引:2
Vesicular lipoproteins (e.g., lipoprotein-X) are found in plasma in cholestasis or following infusion of Intralipid or phospholipid. To investigate the metabolism of vesicular lipoproteins, we isolated them from the plasma of subjects with cholestasis or following chronic or single Intralipid infusion. Cholestasis and chronic Intralipid therapy were found to be associated with elevated plasma concentrations of apoE, as determined by radioimmunoassay. Vesicular lipoproteins purified from each of the three types of plasma contained apoE, as well as other proteins. In cholestasis, in which levels of apoE were up to five times normal, a major portion of the plasma apoE was on vesicular lipoproteins. Normalized for apoE content, all preparations of vesicular lipoproteins displaced 125I-labeled LDL from apoB,E receptors of cultured fibroblasts identically. This displacement was inhibited by monoclonal antibodies that block receptor binding of apoE. Vesicular lipoproteins containing 125I-labeled apoE were internalized and degraded by fibroblasts. Different preparations caused small losses or gains of cellular cholesterol, with appropriate stimulation or suppression of apoB,E receptors. Thus, vesicular lipoproteins contain apoE, and apoE mediates their interaction with the apoB,E receptor. Our results suggest that the catabolism of cholesterol-rich vesicular lipoproteins, formed during cholestasis or following infusions of Intralipid or phospholipid, may be receptor-mediated. 相似文献
5.
The phylogeny of the hominoid primates: a statistical analysis of the DNA-DNA hybridization data 总被引:1,自引:0,他引:1
Sibley and Ahlquist compared the single-copy nuclear DNA sequences of the
hominoid primates using DNA-DNA hybridization. From this data set they
estimated a phylogeny that clusters man and chimpanzees using a distance
Wagner procedure. However, no assessment of statistical confidence in this
estimated phylogeny was made, despite the fact that their data set contains
internal inconsistencies concerning the correct branching order. This paper
presents a modification of Pielou's Q- statistic that allows one to make
nonparametric tests of phylogenetic relationship from distance data. The
results of this analysis indicate that the estimated phylogeny of Sibley
and Ahlquist is without statistical significance owing to the internal
inconsistencies of the data set. A survey and additional analyses of other
types of molecular data indicate that the phylogeny that clusters
chimpanzees and gorillas and has the human lineage splitting off earlier is
statistically consistent with all the molecular data (including the DNA-DNA
hybridization data), whereas the phylogeny estimated by Sibley and Ahlquist
can be rejected at the 5% level using the data on restriction- endonuclease
sites in the mitochondrial genome.
相似文献
6.
Chronic alcohol intake is associated with an increase in fasting plasma high density lipoproteins (HDL). To study alcohol's acute effects on plasma lipoproteins, we measured plasma lipoprotein concentrations and activities of postheparin plasma lipases in nine normolipemic males after ingestion of 40 g of ethanol (as whiskey). After alcohol there was no change in lipoprotein lipase activity but hepatic lipase was decreased to 67% of baseline at 6 hr. There were associated increases in HDL phospholipids (12 mg/dl) and cholesterol (10 mg/dl) resulting in prominence of larger, lipid-enriched HDL particles. Changes were most pronounced in the HDL3 and HDL2a subclasses. Very low density lipoprotein (VLDL) phospholipids and cholesterol were also increased by 13 and 9 mg/dl, respectively, with no significant change in triglycerides. Changes in lipoproteins and lipase were largely reversed 10 hr after alcohol intake. The transient increases in VLDL and HDL lipids after alcohol may result in part from acute inhibition of hepatic lipase activity. The results suggest a role of hepatic lipase in the catabolism of phospholipids of VLDL and possibly HDL. 相似文献
7.
C B Hesler M L Brown D S Feuer Y L Marcel R W Milne A R Tall 《The Journal of biological chemistry》1989,264(19):11317-11325
In an attempt to define an active domain of the protein, fragments of cholesteryl ester transfer protein (CETP) were obtained by limited digestion of the native, plasma-derived protein with trypsin, chymotrypsin, or Staphylococcus aureus V8 protease or by expression of CETP cDNA restriction fragments in Escherichia coli. Although digestion of native CETP with these proteases resulted in extensive fragmentation of the protein and loss of the intact 74-kDa molecule as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, CE transfer activity was unaffected (trypsin or chymotrypsin treatment) or only partially lost (V8 protease treatment). Analysis by molecular sieve chromatography showed that the CE transfer-active product of this proteolysis consisted of polypeptide fragments which remained associated, retaining the native molecular weight of CETP. These proteolyzed complexes were resistant to dissociation by dithiothreitol, 8 M urea, or delipidating agents. As shown by CE transfer activity, native CETP was found to possess a stable conformation which remained unchanged in buffers containing up to 4.5 M urea, or following exposure to even higher (8 M) urea concentrations. CETP polypeptides from bacterially expressed cDNA fragments were found to be catalytically inactive although they contained the epitope for an inhibitory anti-CETP monoclonal antibody and had emulsion binding properties similar to native CETP. Selected synthetic CETP peptides (including the peptide containing the inhibitory monoclonal antibody epitope) were also devoid of CE transfer activity. Thus, no evidence was found for an independently active subunit of the CETP. Together, the results indicate that the CETP possesses a distinct and highly stable tertiary structure which is required for CE transfer catalytic activity. 相似文献
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Dr AR Holmes RD Cannon HF Jenkinson 《Journal of industrial microbiology & biotechnology》1995,15(3):208-213
The yeastCandida albicans coaggregates with a variety of streptococcal species, an interaction that may promote oral colonization by yeast cells.C. albicans andCandida tropicalis are the yeasts most frequently isolated from the human oral cavity and our data demonstrate that both these species bind toStreptococcus gordonii NCTC 7869 while two otherCandida species (Candida krusei andCandida kefyr) do not. Adherence ofC. albicans was greatest when the yeast had been grown at 30° C to mid-exponential growth phase. For 21 strains ofC. albicans there was a positive correlation between the ability to adhere toS. gordonii and adherence to experimental salivary pellicle. Whole saliva either stimulated or slightly inhibited adherence ofC. albicans toS. gordonii depending on the streptococcal growth conditions. The results suggest that the major salivary adhesins and coaggregation adhesins ofC. albicans are co-expressed. 相似文献
10.
Reduced high density lipoprotein cholesterol in human cholesteryl ester transfer protein transgenic mice 总被引:22,自引:0,他引:22
L B Agellon A Walsh T Hayek P Moulin X C Jiang S A Shelanski J L Breslow A R Tall 《The Journal of biological chemistry》1991,266(17):10796-10801
The human cholesteryl ester transfer protein (CETP) facilitates the exchange of neutral lipids among lipoproteins. In order to evaluate the effects of increased plasma CETP on lipoprotein levels, a human CETP minigene was placed under the control of the mouse metallothionein-I promoter and used to develop transgenic mice. Integration of the human CETP transgene into the mouse genome resulted in the production of active plasma CETP. Zinc induction of CETP transgene expression caused depression of serum cholesterol due to a significant reduction of high density lipoprotein cholesterol. There was no change in total cholesterol content in very low and low density lipoproteins. However, there was a decrease in the free cholesterol/cholesteryl ester ratio in plasma and in all lipoprotein fractions of transgenic mouse plasma, suggesting stimulation of plasma cholesterol esterification. The results suggest that high levels of plasma CETP activity may be a cause of reduced high density lipoproteins in humans. 相似文献