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981.
Molecular Cloning and Characterization of a Radial Spoke Head Protein of Sea Urchin Sperm Axonemes: Involvement of the Protein in the Regulation of Sperm Motility 总被引:3,自引:1,他引:2 下载免费PDF全文
Denis Gingras Daniel White Jrome Garin Jacky Cosson Philippe Huitorel Hans Zingg Christian Cibert Claude Gagnon 《Molecular biology of the cell》1998,9(2):513-522
Monoclonal antibodies raised against axonemal proteins of sea urchin spermatozoa have been used to study regulatory mechanisms involved in flagellar motility. Here, we report that one of these antibodies, monoclonal antibody D-316, has an unusual perturbating effect on the motility of sea urchin sperm models; it does not affect the beat frequency, the amplitude of beating or the percentage of motile sperm models, but instead promotes a marked transformation of the flagellar beating pattern which changes from a two-dimensional to a three-dimensional type of movement. On immunoblots of axonemal proteins separated by SDS-PAGE, D-316 recognized a single polypeptide of 90 kDa. This protein was purified following its extraction by exposure of axonemes to a brief heat treatment at 40°C. The protein copurified and coimmunoprecipitated with proteins of 43 and 34 kDa, suggesting that it exists as a complex in its native form. Using D-316 as a probe, a full-length cDNA clone encoding the 90-kDa protein was obtained from a sea urchin cDNA library. The sequence predicts a highly acidic (pI = 4.0) protein of 552 amino acids with a mass of 62,720 Da (p63). Comparison with protein sequences in databases indicated that the protein is related to radial spoke proteins 4 and 6 (RSP4 and RSP6) of Chlamydomonas reinhardtii, which share 37% and 25% similarity, respectively, with p63. However, the sea urchin protein possesses structural features distinct from RSP4 and RSP6, such as the presence of three major acidic stretches which contains 25, 17, and 12 aspartate and glutamate residues of 34-, 22-, and 14-amino acid long stretches, respectively, that are predicted to form α-helical coiled-coil secondary structures. These results suggest a major role for p63 in the maintenance of a planar form of sperm flagellar beating and provide new tools to study the function of radial spoke heads in more evolved species. 相似文献
982.
An Apical-Type Trafficking Pathway Is Present in Cultured Oligodendrocytes but the Sphingolipid-enriched Myelin Membrane Is the Target of a Basolateral-Type Pathway 下载免费PDF全文
Myelin sheets originate from distinct areas at the oligodendrocyte (OLG) plasma membrane and, as opposed to the latter, myelin membranes are relatively enriched in glycosphingolipids and cholesterol. The OLG plasma membrane can therefore be considered to consist of different membrane domains, as in polarized cells; the myelin sheet is reminiscent of an apical membrane domain and the OLG plasma membrane resembles the basolateral membrane. To reveal the potentially polarized membrane nature of OLG, the trafficking and sorting of two typical markers for apical and basolateral membranes, the viral proteins influenza virus–hemagglutinin (HA) and vesicular stomatitis virus–G protein (VSVG), respectively, were examined. We demonstrate that in OLG, HA and VSVG are differently sorted, which presumably occurs upon their trafficking through the Golgi. HA can be recovered in a Triton X-100-insoluble fraction, indicating an apical raft type of trafficking, whereas VSVG was only present in a Triton X-100-soluble fraction, consistent with its basolateral sorting. Hence, both an apical and a basolateral sorting mechanism appear to operate in OLG. Surprisingly, however, VSVG was found within the myelin sheets surrounding the cells, whereas HA was excluded from this domain. Therefore, despite its raft-like transport, HA does not reach a membrane that shows features typical of an apical membrane. This finding indicates either the uniqueness of the myelin membrane or the requirement of additional regulatory factors, absent in OLG, for apical delivery. These remarkable results emphasize that polarity and regulation of membrane transport in cultured OLG display features that are quite different from those in polarized cells. 相似文献
983.
Hans H. Maurer Joachim W. Arlt 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1998,714(2)
A gas chromatography–mass spectrometry (GC–MS) procedure was developed for the detection of 4-hydroxycoumarin anticoagulants and their metabolites in urine as part of a systematic toxicological analysis procedure for acidic drugs and poisons after extractive methylation. The part of the phase-transfer catalyst remaining in the organic phase was removed by solid-phase extraction on a diol phase. The compounds were separated by capillary GC and identified by computerized MS in the full scan mode. Using mass chromatography with the ions m/z 291, 294, 295, 309, 313, 322, 324, 336, 343 and 354, the possible presence of 4-hydroxycoumarin anticoagulants and/or their metabolites could be indicated. The identity of positive signals in such mass chromatograms was confirmed by comparison of the peaks underlying full mass spectra with the reference spectra recorded during this study. This method allowed the detection of therapeutic concentrations of phenprocoumon and warfarin in human urine samples. In absence of human urine, acenocoumarol, coumachlor, coumatetrayl, pyranocoumarin (cyclocumarol) could be detected only in rat urine. 相似文献
984.
Hans Ulrich Stilz Wolfgang Guba Bernd Jablonka Melitta Just Otmar Klingler Wolfgang König Volkmar Wehner Gerhard Zoller 《International journal of peptide research and therapeutics》1998,5(2-3):215-221
Summary Antagonists of the platelet fibrinogen receptor (GP IIb/IIIa receptor) are expected to be a new promising class of antithrombotic
agents. The binding of fibrinogen to the fibrinogen receptor depends on an Arg-Gly-Asp-Ser (RGDS) tetrapeptide recognition
motif. Structural modifications of the RGDS lead have led to the discovery of a non-peptide RGD mimetic GP IIb/IIIa antagonist20 (S 1197). Compound20 inhibits dose-dependently and reversibly human platelet aggregation. Modeling studies based on structure-activity data revealed
the following structural features of the drug as important for receptor binding: the amidino group, the carboxylate group,
hydrophobic substitutions at the carboxyl-terminus and at the side chain carrying the positive charge, the carboxyl-terminal
NH group of the β-amino acid as a hydrogen bond donor and one oxygen atom of the hydantoin as a hydrogen bond acceptor. The
ethyl ester prodrug of20 (S 5740) is an orally active antithrombotic agent which has the potential to be used to treat and prevent thrombotic diseases
in humans. 相似文献
985.
986.
Zhu Genhai Bohnert Hans J. Jensen Richard G. Wildner Günter F. 《Photosynthesis research》1998,55(1):67-74
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) (EC 4.1.1.39) not only catalyzes carboxylation and oxygenation of ribulose-1,5-bisphosphate (RuBP), but it can also act either as an epimerase or isomerase converting RuBP into xylulose-1,5-bisphosphate (XuBP) or 3-ketoarabinitol-1,5-bisphosphate (KABP), respectively, a process called misfire. XuBP is formed as a result of misprotonation at C3 of the RuBP-enediol. It is released from Rubisco active sites and accumulates in the reaction mixture. Increasing the amounts of CO2 or O2 decreases XuBP production. However, KABP synthesis, which has been proposed to be only a product due to C2 misprotonation of the RuBP-endiol, is dependent upon the presence of O2. KABP remains tightly bound to Rubisco active sites after its formation, causing the loss of Rubisco activity (fallover). The results suggest that the non-stabilized form of the peroxy-intermediate in the oxygenase reaction can be converted in a backreaction to KABP and molecular oxygen. The stabilization of the peroxy-intermediate due to the presence of Mn2+ instead of Mg2+ eliminates the formation of KABP. 相似文献
987.
988.
Treatment of the cell wall-less mutant CW 15 of Chlamydomonasreinhardtii with human serum leads to a marked increase of thecell volume, followed by an irreversible cytolysis. Heat-inactivatedserum as a control reveals no cytotoxic effects on CW 15. Experimentswith C4-, properdin-, C3-, and factor H-depleted sera indicatethe alternative pathway of complement as being responsible forthe serum-mediated lysis. After immunofluorescence marking aswell as electromicroscopically after negative staining the membraneattacking complex of complement, C5b-9, could be demonstratedon the surface of CW 15. These results together with the observationthat cells of the wild-type strain 11-32c of C. reinhardtiiare not lysed by active serum suggest that only protoplastsof Chlamydomonas carry surface structures capable to activatethe alternative pathway of complement. In order to find out whether other cell wall mutants of C. reinhardtii,besides CW 15, can also activate the human complement system,we tested three strains each of the three known mutant categories.Strains CW 4, CW 9, and CW 19, representing category A, andstrains CW 3, CW 10, and CW 92, representing category C, andCW 8 and CW 18, accounting for category B, were cytolysed bynormal human serum. Only one type used in our experiments, CW20 of category B, resisted serum treatment, suggesting the needto redefine this category.
1This paper is dedicated to Professor Dr. Andr? Pirson on theoccasion of his 80th birthday (Received December 1, 1989; Accepted April 5, 1990) 相似文献
989.
990.