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21.
Comparison of nonphosphorylated and phosphorylated species of polyomavirus major capsid protein VP1 and identification of the major phosphorylation region. 总被引:14,自引:14,他引:0 下载免费PDF全文
The major virion protein of polyomavirus, VP1, consists of about six isoelectric species designated A through F. The minor species D, E, and F are phosphorylated and are thought to serve as viral receptors. We first wanted to distinguish whether all VP1 species are derived by post-translational modification from a common amino acid sequence or whether one or more of the species contain a region(s) of altered amino acid sequence resulting from alternate mRNA processing. We compared the VP1 species by detailed peptide mapping with several combinations of specific protease and radioisotopic labels. This approach enabled us to examine more than 80% of the predicted VP1 sequence, including the amino-and carboxy-termini. We found no evidence of sequence differences among any of the VP1 species. The specific incorporation of 32Pi was found to be the same for all of the phosphorylated species. Comparison of the phosphorylation sites of in vivo 32Pi-labeled D, E, and F by peptide mapping showed them to be identical. Each phosphorylated species contained a single major phosphopeptide and several minor phosphopeptides. The major phosphoamino acid, identified by acid hydrolysis, was phosphothreonine, with phosphoserine also present. By using chemical cleavage methods, we localized the major phosphorylation region to a central portion of the VP1 sequence. We discuss some features of this region and relate this information to functional implications of phosphorylation. 相似文献
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Anders Fjose Ian F. Pryme Johan R. Lillehaug 《Molecular and cellular biochemistry》1983,56(2):137-144
Summary After transfer of Krebs II ascites cells from the mouse peritoneum to suspension culture addition of the phorbol ester 12-0-tetradecanoyl-phorbol-13-acetate (TPA) causes an early stimulation of 3H-choline incorporation into phosphatidylcholine (PC). Choline transport into the treated cells, however, was unaffected. Within 30 min of TPA treatment 3H-choline incorporation was almost 300% above the control level. During a 5 hr period of suspension culture the overall patterns of 3H-choline incorporation were similar in TPA-treated and control cultures though the rate was greatly accentuated by the presence of the phorbol ester. Incubation of cells with cycloheximide prior to incubation with TPA did not result in an inhibition of the TPA-directed 3H-choline incorporation. After 3 hr incubation with TPA there were large increases in radioactivity in all subcellular fractions. At 20 hr, however, the values were not far from those of the control. During the first 3 hr of incubation with TPA the incorporation of 3H-choline into light rough (LR) and smooth (S) membranes was stimulated to levels of 400% and 320% respectively above control values. At later times the profiles of radioactivity in membrane subfractions in TPA-treated and control cultures were similar. The results illustrate an early effect of TPA on PC biosynthesis in Krebs II ascites cells while at later times of incubation the stimulatory effect was virtually abolished. 相似文献
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Purification and partial characterization of four proteins from human parotid saliva 总被引:15,自引:7,他引:8 下载免费PDF全文
Four proteins, which have been designated A, B, C and D, have been purified from human parotid saliva. These proteins are the major constituents of parotid saliva which migrate rapidly to the anode in polyacrylamide electrophoresis at pH9.5. Gel filtration and polyacrylamide electrophoresis were employed in the purification procedures. After purification all four preparations were tested for homogeneity by electrophoresis at pH2.8 and 9.5, by isoelectric focusing in the pH range 3-10, by immunodiffusion, and by sedimentation in the analytical ultracentrifuge. None of the proteins showed significant activity in assays for amylase, acid and alkaline phosphatase, protease, lysozyme, ribonuclease, peroxidase, beta-glucuronidase, beta-galactosidase, iron-binding activity and esterase. No cross-reactions were detected with antisera specific for lactoferrin and 15 serum proteins. All four proteins were rich in glutamic acid, proline and glycine and were lacking completely the sulphur-containing amino acids. Proteins A and C contained no threonine or tyrosine. Carbohydrate could be demonstrated only in protein A at a concentration of 4% of the total protein. 相似文献
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Preparative thin-layer and column chromatography of prostaglandins 总被引:15,自引:0,他引:15
N H Anders 《Journal of lipid research》1969,10(3):316-319
Chromatographic methods are used to identify various monounsaturated PGs (prostaglandins). TLC (thin-layer chromatography) and column chromatography are described in detail. These systems were developed specifically for separating epimers of PGE1 and PGF1, but they are useful in separating some of the known natural PGs as well. A table presents information on identification of the various PGs with neutral silica and acidic silica. The results of these laboratory experiments indicate that 1 ug-1g of PG can be purified by chromatographic methods with little or no loss due to irreversible adsorption or rearrangement if proper precautions and solvent systems are used. TLC seems to be useful in distinguishing diastereomers of PGs. Relative mobilities of the various hydroxy diastereomers are not changed by the solvent systems or by esterification. 相似文献
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Summary Labelling of renal tubule cytosomes with electron dense iron granules can be attained by daily intramuscular injections to mice of an iron sorbitol citric-acid compound in a total of approximately 50 mg Fe+++/100 g of body weight. The labelled cytosomes correspond to secondary lysosomes and represent heterolysosomes or ambilysosomes. The evidence suggests that tubule and lysosome function are undisturbed by the labelling procedure. The use of this method for fine structural studies of the interaction between secondary lysosomes and other cytoplasmic organelles and elements is indicated.Microbodies do not incorporate administered Fe+++. The morphological observations support the opinion that these bodies are formed in specialized portions of the smooth surfaced endoplasmic reticulum of proximal tubule cells.Supported in part by grants from the Swedish Medical Research Council (Projects No. K 67-12x-1006-2, B 67-12x-1006-02K, K 68-12x-1006-03, and B 69-12x-1006-04A). The assistance of Miss Silwa Mengarelli and Miss Britt-Marie Pettersson is gratefully acknowledged. 相似文献
29.
From a previously published theory (Israelsson and Johnsson 1967) for circumnutations in Helianthus annuus it is possible to predict the geotropical curvatures of the hypocotyls. This extension of the theory is given in the present paper and some geotropical experiments are performed and discussed. The agreement between the theory and the experiments has been verified in the case of gravitational stimulation during relatively short stimulation periods, in the case of continuous gravitational stimulation, etc. Restrictions in the proposed model are discussed. 相似文献
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