| 11. |
- Lilja, Hans, et al.
(författare)
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Semenogelin, the predominant protein in human semen. Primary structure and identification of closely related proteins in the male accessory sex glands and on the spermatozoa
- 1989
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Ingår i: Journal of Biological Chemistry. - 0021-9258. ; 264:3, s. 900-1894
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Tidskriftsartikel (refereegranskat)abstract
- The predominant protein in human semen, semenogelin, was characterized by lambda gt11 clones isolated from a seminal vesicular cDNA library. One clone, carrying a cDNA insert of 1606 nucleotides and a polyadenylated tail, coded for the entire semenogelin precursor. An open reading frame of 1386 nucleotides encodes a signal peptide and the mature protein of 439 amino acid residues, in which residues 85-136 are identical with a previously characterized semenogelin fragment. The polypeptide chain displays a most conspicuous region of internal sequence homology where 46 of the 58 amino acid residues at positions 259-316 are repeated at positions 319-376. An abundant seminal vesicular transcript of 1.8 kilobases (kb) codes for semenogelin. Two additional transcripts, one seminal vesicular 2.2-kb species and one epididymal 2.0-kb species, code for related proteins that have a close structural relationship as well as antigenic epitopes in common with semenogelin. Semenogelin and the semenogelin-related proteins are the major proteins involved in the gelatinous entrapment of ejaculated spermatozoa. Antigenic epitopes common to these proteins are localized to the parts of the spermatozoa involved in locomotion. The spermatozoa become progressively motile as the gel-forming proteins are fragmented by the kallikrein-like protease, prostate-specific antigen, and the gel dissolves.
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| 12. |
- Lohmander, Stefan, et al.
(författare)
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Xylosyl transfer to the core protein precursor of the rat chondrosarcoma proteoglycan
- 1989
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Ingår i: Journal of Biological Chemistry. - 0021-9258. ; 264:31, s. 18775-18780
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Tidskriftsartikel (refereegranskat)abstract
- Rat chondrosarcoma chondrocytes were labeled with [3H]serine or [3H]mannose as a precursor. Intracellular proteoglycan core protein precursor was purified from cell lysates by immunoprecipitation with polyclonal antibodies against the hyaluronic acid-binding region, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The core precursor was eluted from the gels and treated with alkaline borohydride in order to convert serine residues substituted with xylose or N-acetylgalactosamine to alanine (or with alkaline sulfite to convert them to cysteic acid). After acid hydrolysis, the proportions of labeled serine and alanine (or cysteic acid) were determined by high performance liquid chromatography, and the results were compared with those obtained for the completed proteoglycan molecules isolated from the same cultures. In the completed proteoglycans, about 55% of the serine residues were substituted with xylose or N-acetylgalactosamine, while the corresponding figure for the intracellular precursor molecules was less than 5%. These results indicate, in agreement with our previous kinetic data, that the major part of the xylosyl transfer to the chondrosarcoma proteoglycan core protein precursor must occur late in the processing sequence, i.e. after about 85% of its intracellular lifetime and no more than 7 min before the addition of the rest of the chondroitin sulfate chain. The ratio of [3H]mannose to [3H]fucose in the core precursor was about 19, while that for the complete proteoglycan was about 2. This indicates the presence of high mannose, N-linked oligosaccharides on the core protein precursor which are converted to the complex forms on the completed proteoglycan. These data provide further support that the core precursor resides mainly in the pre-Golgi compartment and that xylosylation occurs mainly in a Golgi compartment.
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| 13. |
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| 14. |
- Nilsson Ekdahl, Kristina, et al.
(författare)
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Fructose-1,6-bisphosphatase from rat liver. A comparison of the kinetics of the unphosphorylated enzyme and the enzyme phosphorylated by cyclic AMP-dependent protein kinase.
- 1985
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 260, s. 14173-14179
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Tidskriftsartikel (refereegranskat)abstract
- A purification procedure for rat hepatic fructose-1,6-bisphosphatase, described earlier, has been improved, resulting in an enzyme preparation with a neutral pH optimum and with both phosphorylatable serine residues present. The subunit Mr was 40,000. Phosphorylation in vitro with cyclic AMP-dependent protein kinase resulted in the incorporation of 1.4 mol of phosphate/mol of subunit and led to an almost 2-fold decrease in apparent Km for fructose-1,6-bisphosphate. In contrast to yeast fructose-1,6-bisphosphatase, fructose-2,6-bisphosphate had no effect on the rate of phosphorylation or dephosphorylation of the intact enzyme. The effects of the composition of the assay medium, with regard to buffering substance and Mg2+ concentration, on the apparent Km values of phosphorylated and unphosphorylated enzyme were investigated. The kinetics of phosphorylated and unphosphorylated fructose-1,6-bisphosphatase were studied with special reference to the inhibitory effects of adenine nucleotides and fructose-2,6-bisphosphate. Unphosphorylated fructose-1,6-bisphosphatase was more susceptible to inhibition by both AMP and fructose 2,6-bisphosphate than phosphorylated enzyme, at high and low substrate concentrations. Both ATP and ADP had a similar effect on the two enzyme forms, ADP being the more potent inhibitor. Finally, the combined effect of several inhibitors at physiological concentrations was studied. Under conditions resembling the gluconeogenic state, phosphorylated fructose-1,6-bisphosphatase was found to have twice the activity of the unphosphorylated enzyme.
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| 15. |
- Nilsson Ekdahl, Kristina
(författare)
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Rat liver fructose-1,6-bisphosphatase: Identification of serine- 338 as a third major phosphorylation site for cyclic AMP-dependent protein kinase. Activity changes associated with multisite phosphorylation in vitro
- 1987
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 262, s. 16699-16703
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Tidskriftsartikel (refereegranskat)abstract
- Rat liver fructose-1,6-bisphosphatase was phosphorylated with [32P]ATP and the catalytic subunit of cyclic AMP-dependent protein kinase. After digestion with trypsin, two peptides were isolated containing 68 and 32% of the total radioactivity, respectively. The former was found to contain the sequence Ala-Lys-Ser(P)-Arg-Pro-Ser(P)-Leu-Pro. In this fragment, Ser-341, but not Ser-338, had earlier been reported to be a phosphorylation site. The other peptide contained phosphorylated Ser-356. It was demonstrated that all the protein-bound [32P]phosphate was distributed evenly between these three serines in the native enzyme regardless of the degree of phosphorylation. Preservation of the three-dimensional structure, however, was needed to obtain phosphorylation of Ser-356. Peptides containing each phosphorylatable serine residue were sequentially removed by digesting the enzyme with chymotrypsin which cleaved off Ser-356, denaturing it with urea, digesting it further with chymotrypsin, thus removing Ser-341, and finally treating it with trypsin which eliminated the rest of the radioactivity which was bound to Ser-338. Kinetic studies of fructose-1,6-bisphosphatase digested in this manner revealed that phosphorylation of Ser-338 decreased the apparent Km for fructose 1,6-bisphosphatase, whereas phosphorylation of Ser-341 decreased the inhibitory effect of AMP and fructose 2,6-bisphosphatase, Phosphorylation of Ser-356 did not affect these parameters.
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| 16. |
- Ny, Tor, et al.
(författare)
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Regulation of tissue-type plasminogen activator activity and messenger RNA levels by gonadotropin-releasing hormone in cultured rat granulosa cells and cumulus-oocyte complexes.
- 1987
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 262:24, s. 11790-3
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Tidskriftsartikel (refereegranskat)abstract
- Gonadotropin-releasing hormone (GnRH) acts directly on the ovary to induce ovulation in hypophysectomized proestrous rats. Because plasminogen activators (PAs) are implicated in gonadotropin-induced ovulation, we have studied the effect of GnRH on ovarian PA synthesis. GnRH induced tissue-type PA (tPA) secretion by cultured rat granulosa cells, but inhibited the secretion of urokinase-type PA. These effects were blocked by co-treatment with a GnRH antagonist, suggesting that stereospecific GnRH receptors are involved. Follicle-stimulating hormone (FSH) also induced tPA in granulosa cells but with a different time course than GnRH; the combined effect of FSH and GnRH was additive. The GnRH effect was mimicked by the calcium- and phospholipid-dependent protein kinase C activator, phorbol myristate acetate. In isolated cumulus-oocyte complexes and cumulus cells, GnRH treatment also increased tPA activity. In contrast, treatment of denuded oocytes with GnRH did not increase enzyme activity. After GnRH stimulation of the cumulus-oocyte complexes, tPA content in the denuded oocyte was elevated, suggesting that the cumulus cells mediate the action of GnRH to increase the oocyte enzyme levels. Hybridization experiments using a labeled rat tPA-specific DNA probe showed that both FSH and GnRH increased the level of tPA mRNA in cultured granulosa cells; the stimulatory effect of GnRH was blocked by the GnRH antagonist. Our results indicate that GnRH treatment increases tPA secretion by cultured granulosa cells and cumulus-oocyte complexes. The stimulation of enzyme activity in the granulosa cells is accompanied by increases in tPA mRNA levels.
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| 17. |
- Spyrou, Giannis, et al.
(författare)
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Compartmentation of dCTP pools. Evidence from deoxyliponucleotide synthesis
- 1987
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Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 262:34, s. 16425-16432
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Tidskriftsartikel (refereegranskat)abstract
- The nucleotide fraction of cultured 3T6 and 3T3 mouse fibroblasts contains deoxy-CDP choline and deoxy-CDP ethanolamine as well as the corresponding riboliponucleotides. In permeabilized cells both deoxyliponucleotides were formed from dCTP. In intact cells they could be labeled from [5-3H] deoxycytidine or cytidine via transformation of the nucleosides to dCTP. Their turnover was slow compared to that of dCTP. When rapidly growing 3T3 cells were labeled during 90 min from deoxycytidine the specific activity of dCDP choline was 2.4 times higher than that of dCTP while after labeling from cytidine both nucleotides (and CTP) reached the same specific activity under steady state conditions. Also dCDP ethanolamine was labeled more rapidly from deoxycytidine than from cytidine. Our results suggest that the deoxyliponucleotides were synthesized from a dCTP pool that was labeled preferentially from deoxycytidine. Earlier work (Nicander, B., and Reichard, P. (1983) Proc. Natl. Acad. Sci. U. S. A. 80, 1347-1351) had demonstrated synthesis of DNA from a dCTP pool labeled preferentially from cytidine. Taken together our results suggest that deoxyliponucleotides and DNA are synthesized from separate dCTP pools.
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| 18. |
- Spyrou, Giannis, et al.
(författare)
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Intracellular compartmentation of deoxycytidine nucleotide pools in S phase mouse 3T3 fibroblasts
- 1989
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Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 264:2, s. 960-964
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Tidskriftsartikel (refereegranskat)abstract
- We labeled mouse 3T3 fibroblasts, synchronized in G0 or S phase, from [3H]cytidine or [3H]deoxycytidine and measured the flow of isotope into and through deoxycytidine nucleotide pools, including the two deoxyliponucleotides dCDP choline and dCDP ethanolamine. Compared to G0 cells, S phase cells had much larger pools with a 20-40-fold faster turnover. The dCTP pool of S phase cells during steady state conditions attained a 6-fold higher specific activity than the pool of G0 cells when labeled from cytidine but a 10-fold lower specific activity when labeled from deoxycytidine. The dCTP pool of G0 cells showed a slow but measurable turnover indicating a limited amount of de novo synthesis also in resting cells. The labeling pattern of dCTP and deoxyliponucleotides of G0 cells was compatible with a simple precursor-product relationship. In S phase cells, however, dCDP choline had a 4-6 times higher specific activity during steady state conditions than dCTP and dCMP when the cells were labeled with [3H]deoxycytidine. We suggest that 3T3 cells contain two distinct intracellular dCTP pools, one labeled preferentially from cytidine and used for DNA replication, the other labeled from deoxycytidine and used for deoxyliponucleotide synthesis. We speculate that the latter pool during S phase may be temporarily sequestered in the cell's membrane fraction before equilibration with the much larger dCTP pool originating in S phase cells from the reduction of CDP.
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| 19. |
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| 20. |
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