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161.
We have compared the amino acid sequences of two low-molecular-weight avian apoproteins: apoVLDL-II from very low-density lipoproteins of hen plasma and apovitellenin I from hen egg yolk. The sequence of White Leghorn apoVLDL-II was derived from the nucleotide sequence of cloned apoVLDL-II DNA (Chan et al., 1980). The sequenator was used to determine the amino acid sequence of apovitellinin I from two breeds of hen (White Leghorn and Australorp). The sequences from the two breeds were not only identical, but they also completely matched the predicted sequence derived from the apoVLDL-II DNA sequence. The identity reported here establishes that this protein is transported intact from the blood to the egg yolk. 相似文献
162.
Two mutator genes of mammalian cells were demonstrated. One was associated with the ribonucleoside diphosphate reductase, and the other was associated with an extreme adenosine sensitivity. 相似文献
163.
T. T. Tchen Samuel W. Chan Tuan H. Kuo K. M. Mostafapour Victoria H. Drzewiecki 《Molecular and cellular biochemistry》1977,15(2):79-87
Summary Biochemical and ultrastructural studies indicate that the atrophy of adrenal cortex in hypoyhysectomized rats involves the following changes: (1) One to two days after hypophysectomy, there is loss of template activity resulting from cumulative DNA-damage and heterochromatinization.In vivo ACTH-administration led to recuperation of these cells, indicating damage during hypophysectomized state to be reversible. (2) If the duration of hypophysectomy is prolonged, some of the cells become irreversibly damaged and can no longer recuperate afterin vivo ACTH administration. (3) The period of most rapid cell death is from the third to seventh day after hypophysectomy. The cause of cell death is probably due to membrane damage in the absence of protein synthesis, leading to lysis of the cells. Lysozomes and macrophages are apparently not involved.Supported by U.S.P.H.S. grants AM-5384 and AM-13724 and taken in part from dissertations submitted by Chan and by Mostafapour to Wayne State University in partial fulfillment towards the Ph.D. degree.An invited article. 相似文献
164.
Native aspartate transcarbamoylase from Escherichia coli was modified with the bifunctional reagent tartaryl diazide in the presence of the substrate carbamoyl phosphate and the substrate analog succinate. The product had the same sedimentation coefficient as the native enzyme but showed a marked increase in affinity for the substrate aspartate with a hyperbolic saturation curve. The Michaelis constant for aspartate (7.4 mM) is similar to that estimated for the relaxed state of the enzyme. The high substrate affinity was not produced if modification was conducted in the absence of substrate analogs or with a monofunctional reagent. The modified enzyme was also desensitized towards the allosteric effectors ATP and CTP. It appears to represent a stabilized relaxed state whose conversion to the taut state is presumably prevented by cross-linking. 相似文献
165.
The structure and the orientation of cytochrome c oxidase molecules in crystalline cytochrome c oxidase membranes (Vanderkooi, G., Senior, A.E., Capaldi, R.A., and Hayashi, H. (1972) Biochim. Biophys. Acta 274, 38-48) were studied by image analysis of electron micrographs and by reacting the crystalline preparations with immune gamma-globulins against individual cytochrome c oxidase subunits. Binding of gamma-globulins to the membranes was detected by the following two methods: (a) electrophoretic identification of gamma-globulin polypeptides in the washed membranes; (b) electron microscopic examination of the negatively stained membranes. The membranes bound immune gamma-globulins against subunit IV (which faces the matrix side in intact mitochondria) but failed to bind immune gamma-globulins against subunits II + III (which face the outer side of the inner membrane in intact mitochondria). In contrast, solubilized cytochrome c oxidase bound either of the two immune gamma-globulins. All cytochrome c oxidase molecules in the crystalline membranes are thus asymmetrically arranged so that subunit IV faces outward and subunits II + III face toward the interior. This orientation is opposite to that found with intact mitochondria. The data also suggest that the crystalline membranes form closed vesicles which are impermeable to externally added gamma-globulins. 相似文献
166.
Membrane protein synthesis in embryonic chick erythroid cells 总被引:4,自引:0,他引:4
167.
Association of long surface appendages with adherence-related functions of the gram-positive species Actinomyces naeslundii 总被引:18,自引:3,他引:15 下载免费PDF全文
Electron microscopy of new isolates of gram-positive Actinomyces naeslundii demonstrated long, fragile appendages. Removal of the appendages impaired attachment to epithelial cells and reaggregation, thus implicating them in attachment-related functions. 相似文献
168.
Radhey S. Gupta David Y. H. Chan Louis Siminovitch 《Journal of cellular physiology》1978,97(3):461-467
The hypothesis of functional hemizygosity has been examined for the α-amanitin resistant (AmaR, a codominant marker) locus in a series of Chinese hamster cell lines. AmaR mutants were obtained from different cell lines, e.g., CHO, CHW, M3-1 and CHO-Kl, at similar frequencies. After fractionation of different RNA polymerase activities in the extracts by chromatographic procedures, the sensitivity of the mutant RNA polymerase II towards α-amanitin was determined. While all of the RNA polymerase II activity in mutant CHO and CHO-Kl lines became resistant to α-amanitin inhibition, only about 50% of the activity is highly resistant in AmaR mutants of CHW and M3-1 cell lines. The remaining activity in the latter cell lines shows α-amanitin sensitivity similar to that seen with the wild-type enzyme. This behaviour is similar to that observed with a 1:1 mixture of resistant and sensitive enzymes from CHO cells. These results, therefore, strongly indicate that while only one functional copy of the gene affected by α-amanitin is present in CHO and CHO-Kl cells, two copies of this gene are functional in the CHW and M3-1 cell lines. 相似文献
169.
Antibiotic activity against Heliothis virescens was found in flower buds of Gossypium hirsutum, experimental stock Texas 254. Relatively low antibiotic activity was found in hexane extract, high activity in methanolic extract and residue, and no activity in acetone and water extracts. A condensed tannin having a molecular weight of 4850 was isolated from methanolic extract by column chromatography on Sephadex G-25. It was the major antibiotic component, 3.4% of the dried flower bud. The condensed tannin at 0.2% in the diet retarded larval growth by 84%. 相似文献
170.
Rats weighing 100 g were made chronically uremic by partial left renal artery ligation and contralateral nephrectomy. Rats with urea clearances below 0.30 ml/min and sham-operated controls were pair-fed arginine-free diets, diets containing normal amounts of arginine or diets with high levels of arginine. After 4 to 8 weeks, rats were killed and plasma levels of arginine, ornithine and lysine were measured. In addition, activities of various urea cycle enzymes in liver and kidney and renal transamidinase were determined. Plasma amino acid levels and enzyme activities of the urea cycle remained constant in control rats fed diets differing in arginine content. However, renal transamidinase activity was elevated in control rats fed arginine-free diets. In plasma of uremic as compared with control rats, arginine levels varied with the arginine intake, and lysine levels were elevated when arginine supplements were fed. With all diets, plasma ornithine remained constant in uremic rats at slightly but not significantly increased levels. Hepatic carbamoyl phosphate synthetase activity and renal arginine synthetase activity were reduced in uremic as compared to control rats. Renal transamidinase activity, expressed per g of kidney, was elevated in uremic rats with all diets except arginine-free. When amino acid diets were fed, hepatic arginase activity was higher in uremic rats and this increase was enhanced by arginine-free diets. Other enzyme activities in uremic rats were not affected by the amount of arginine in the diet. 相似文献