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排序方式: 共有396条查询结果,搜索用时 15 毫秒
1.
Werner E.C. Muller Jürgen Conrad Rudolf K. Zahn Renate Steffen Gerhard Uhlenbruck Isabel Miller 《Differentiation; research in biological diversity》1984,26(1-3):30-35
Abstract. The Hexactinellida sponge Aphrocallistes vastus contains a soluble aggregation factor (AF) whose purification has been described in this communication. It is characterized by a S°20.w value of 37 and a buoyant density of 1.45 g/cm3 . The AF is a glycoporteinaceous particle composed of three major protein species; no core structure could be visualized. In the presence of Ca2+ , the AF causes secondary aggregation of single cells. The aggregation process is temperature, pH, and ionic strength independent within a broad range. Evidence is presented indicating that two (or more) AF molecules are required for the establishment of a stable cell: cell interaction. In contrast to the AFs from demosponges, the hexactinellid AF functions species-unspecifically. 相似文献
2.
B Kurelec S Britvi? S Krca W E Müller R K Zahn 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1987,86(1):17-22
Postmitochondrial fractions from marine sponges Geodia cydonium, Tethya aurantium, Verongia aerophoba and Pellina semitubulosa activate precarcinogenic aromatic amine 2-aminoanthracene, but not precarcinogenic polycyclic aromatic hydrocarbon benzo(a)pyrene, to Salmonella typhimurium TA 98 mutagens. All four sponge species lack a benzo(a)pyrene monooxygenase activity, but possesses the enzyme activity whose characteristics (selective activation of aromatic amines, NADPH-dependency, pH optimum at 8.4) are similar to FAD-containing monooxygenase. Tethya postmitochondrial fraction possesses an UDP-glucuronyl transferase activity which catalyzes the conjugation of a considerable part of metabolized 2-acetylamino [9-14C]fluorene to water soluble glucuronides. The possible ecological significance of exuded aromatic amine metabolites as well as the significance of the presence of the selective potential for the activation of aromatic amines to mutagens among sponges for our understanding of the fate and effects of carcinogens in the marine environment are discussed. 相似文献
3.
The lambda O and P gene products are required for the initiation of lambda DNA replication. In order to study the biochemistry of this process, we have constructed plasmids that carry the lambda O gene, P gene, and half of the O gene coding for the amino-terminal half of the O protein. Each is under the control of the inducible lambda promoter, PL. We have purified these three proteins from induced cells carrying the plasmids. Our results show that the amino-terminal portion of the O protein binds to the lambda origin of replication in a manner similar to the intact lambda O protein, demonstrating that the amino-terminal portion of O protein contains the DNA binding domain. Using chromatographic procedures, we have isolated a complex of lambda O and P proteins with lambda dv DNA. The amino-terminal portion of the O protein does not complex with P protein under the same conditions. This suggests that the specificity of the lambda O protein for P protein resides in the carboxyl-terminal half of the lambda O protein. Our results also show that, while the intact O protein is active in in vitro replication of lambda dv plasmid DNA, the amino-terminal portion of the O protein is inactive and is a competitive inhibitor of the lambda O protein in this reaction. These results confirm previous genetic observations that were interpreted as indicating a bifunctional structure for the lambda O protein with the amino-terminal domain recognizing the lambda origin of replication and the carboxyl-terminal domain interacting with the lambda P protein. 相似文献
4.
Identification and isolation of the primary aggregation factor from the cell membrane of the sponge Geodia cydonium 总被引:1,自引:0,他引:1
Prof. Dr. Werner E. G. Müller Jürgen Conrad Rudolf K. Zahn Monika Gramzow Branko Kurelec Gerhard Uhlenbruck 《Molecular and cellular biochemistry》1985,67(1):55-64
Summary The primary aggregation factor (pAF) of sponge cells is a glycoprotein that is firmly associated with the cell membrane. Polyspecific antibodies (anti-GM) prepared from sera raised against membranes of cells from the siliceous sponge Geodia cydonium were found to inhibit initial aggregation of homologous cells. The inhibition of aggregation, caused by anti-GM was neutralized by pAF. The pAF had been successfully solubilized and enriched by affinity chromatography, gel filtration and density gradient centrifugation, if checked by polyacrylamide gel electrophoresis in the presence of urea. The Mr of the native pAF was approximately 40 000 as estimated by gel filtration; under denaturing conditions three protein species (Mr: 16 500, 15 500 and 13 500) were identified in the pAF preparation. The pAF was precipitable by Ca++ and did not cross-react with antisera against homologous purified secondary aggregation factor and lectin. It is mainly composed of protein (48.0%) and carbohydrate (50.2%). The isolated pAF restored the aggregation potency not only of factor-depleted Geodia cells but also of cells from other Demospongiae. However, the pAF displayed no aggregation enhancing effect on urea-treated cells from species belonging to the Calcispongiae or Hexactinellida. We hypothesize that in contrast to the secondary aggregation, the initial aggregation of Geodia cells is mediated by the one-component system, the bivalent and bifunctional pAF. 相似文献
5.
The ribosomal population of the sponge Geodia cydonium has been examined. The monosomes have a sedimentation constant of 80 S, the sizes of the subunits are approximately 60 S and 45 S respectively. The polyribosomes contain up to 40 ribosomal units. Cell free protein synthesizing systems (cell homogenate as well as reconstituted system) have been prepared and characterized with respect to Mg2+, KCI and ATP concentrations, temperature, pH and time course of the reaction. In the cell-free system and in the cellular system the protein biosynthesis is inhibited by chloramphenicol. It is not affected by cycloheximide. 相似文献
6.
7.
W. Reisch Klinkowski K. Wuttky Frilz-Paul Zahn H. Schmalz H. B. Schmidt Rieger A. Rieth Alfred Lein 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1960,30(5):209-212
Ohne Zusammenfassung 相似文献
8.
Modulation of lambda integrase synthesis by rare arginine tRNA 总被引:6,自引:1,他引:5
Lambda's int gene contains an anomalously high frequency of the rare arginine codons AGA and AGG when compared to genes of Escherichia coli or to the rest of phage lambda. These are the least frequent codons in genes of E. coli and are recognized by the rarest tRNAs. The presence of these codons reduces the translation rate and, depending on the context, this can strongly modulate translational efficiency by a variety of mechanisms. In this study, we show that expression of the natural int gene may also be modulated by rare arginine codon usage, and we explore this mechanism. 相似文献
9.
10.
W E Müller J Arendes B Kurelec R K Zahn I Müller 《The Journal of biological chemistry》1977,252(11):3836-3842
The sialyltransferase (= glycoprotein-sialic acid transferase) was studied in the sponge Geodia cydonium, a mesozoan organism. The experiments were performed both in intact cellular and in isolated enzyme systems. It is shown, that desialylated cells show a lower aggregation potency than the controls. During aggregation enzymic sialylation of desialylated sponge cells occurs in the presence of an aggregation factor, which is associated with a high molecular weight particle. The sialylation process is temperature-dependent and can be inhibited by N-ethylmaleimide. Sialylation occurs predominantly at a distinct cell surface component, the aggregation receptor. The sialyltransferase was isolated and purified by the following steps: Sepharose 4B, CM-cellulose, Nonidet treatment, and Sephadex G-100. By this procedure the enzyme was purified 680-fold with a 31% yield. The sialyltransferase is originally associated with the high molecular weight particle also carrying the aggregation factor. In the last step the aggregation factor was separated from the sialyltransferase. The enzyme catalyzes the transfer of sialic acid from CMP-sialic acid to the desialylated aggregation receptor. The molecular weight of the sialyltransferase has been determined to be 52,000. Kinetic studies revealed no lag phase and a dependence on enzyme concentration. The purified transferase has a pH optimum of 7.75 and requires 200 mM NaCl for activity. No requirement for Mg2+ or Ca2+ could be observed. The reaction is inhibited by 10 micronM N-ethylmaleimide. 相似文献