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51.
We have previously shown that nonmuscle caldesmon copurified with brain microtubules binds to microtubules in vitro [Ishikawa et al.: FEBS Lett. 299:54-56, 1992]. To explore the role of caldesmon in the functions of microtubules, further characterization was performed using smooth muscle caldesmon, whose molecular structure and function have been best-characterized in all caldesmon species. Smooth muscle caldesmon bound to microtubules with a stoichiometry of five tubulin dimers to one molecule of caldesmon with the binding constant of 1.1 x 10(6) M-1. The binding of caldesmon to microtubules was inhibited in the presence of Ca2+ and calmodulin. Partial digestion of the caldesmon with alpha-chymotrypsin revealed that the binding site of the caldesmon for microtubules lay in the 34-kDa C-terminal domain. When the caldesmon was in the dimeric form in the absence of a reducing agent, the caldesmon cross-linked microtubules to form bundles. Further, the caldesmon potentiated the polymerization of tubulin, and inhibited the in vitro movement of microtubules on dynein. These results suggest that caldesmon may be involved in the regulation by Ca2+ of the functions of microtubules. 相似文献
52.
Responses of seed germination to salinity were examined using 37 species collected from salt marshes, cliffs, and fore (unstable)
and hind (stable) sand dunes along Japanese coasts. For comparison, seed germination of nine inland species was also examined.
The soil salinities in salt marshes ranged from 150 to 300 mmol/L NaCl, whereas those in fore and hind dunes ranged from 0
to 150 mmol/L NaCl, with a few exceptions. Cliff soils showed relatively high salinities up to 300 mmol/L NaCl. Ciff and foredune
soils that encountered a typhoon and storm showed high salinities >300 mmol/L NaCl. Salt tolerance in seed germination of
coastal plants was ordered by comparing the responses of percentage and rate of germination to salinity conditions up to 200
mmol/L NaCl, being in the order of salt marsh>cliff>foredune≅hind dune≅inland. Thse results indicate that salt tolerance in
seed germination of coastal plants is closely related to the salinity conditions of their habitats. Germination experiments
under favorable conditions showed that a high percentage of the seeds of salt marsh species germinate rapidly, those of diff
species germinate slowly and those of foredune species exhibit a low percentage and low rate of germination. It seems that
these germination characteristics contribute to the success of germination at the ‘safe site’ and the subsequent survivorship
of emerged plants in their natural habitats. 相似文献
53.
Cloning of the alpha-amylase cDNA of Aspergillus shirousamii and its expression in Saccharomyces cerevisiae. 总被引:2,自引:0,他引:2
I Shibuya G Tamura T Ishikawa S Hara 《Bioscience, biotechnology, and biochemistry》1992,56(2):174-179
alpha-Amylase cDNA was cloned and sequenced from Aspergillus shirousamii RIB2504. The putative protein deduced from the cDNA open reading frame (ORF) consisted of 499 amino acids with a molecular weight of 55,000. The amino acid sequence was identical to that of the ORF of the Taka-amylase A gene of Aspergillus oryzae, while the nucleotide sequence was different at two and six positions in the cDNA ORF and 3' non-coding regions, respectively, so far determined. The alpha-amylase cDNA was expressed in Saccharomyces cerevisiae under the control of the yeast ADH1 promoter using a YEp-type plasmid, pYcDE1. The cDNA of glucoamylase, which was previously cloned from the same organism, was also expressed under the same conditions. Consequently, active alpha-amylase and glucoamylase were efficiently secreted into the culture medium. The amino acid sequence of the N-terminal regions of these enzymes purified from the yeast culture medium confirmed that the signal sequences of these enzymes were cleaved off at the same positions as those of the native enzymes of A. shirousamii. 相似文献
54.
Role of de novo protein synthesis in target cells recognized by cytotoxic T lymphocytes specific for vesicular stomatitis virus.
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The requirements for viral and host protein synthesis in the generation of target antigens for cytotoxic T lymphocytes (CTL) was evaluated by using vesicular stomatitis virus (VSV) inactivated by UV irradiation (UV-VSV). EL4 target cells incubated with UV-VSV were recognized and lysed by anti-VSV CTL, indicating that de novo synthesis of viral proteins was not required for the generation of antigens recognized by antiviral CTL. Anti-VSV CTL from H-2b mice primarily recognize determinants derived from the VSV N protein bound to the class I major histocompatibility complex (MHC) antigen H-2Kb. Comparison of a cloned CTL line representing this specificity and a heterogeneous population of anti-VSV CTL showed that determinants other than that recognized by the cloned CTL were generated more efficiently from UV-VSV. By using vaccinia virus recombinants that express deletion fragments of the N protein, it was shown that these additional determinants were probably derived from VSV proteins other than the N protein. The protein synthesis inhibitor emetine was used to determine whether newly synthesized host proteins were required for antigen generation. The addition of emetine to target cells prior to or at the time of the addition of UV-VSV inhibited lysis by anti-VSV CTL. This inhibition could be due to depletion of newly synthesized MHC molecules from intracellular membranes. This hypothesis was supported by using brefeldin A to delay membrane protein transport in target cells during the time of incubation with emetine and UV-VSV, which resulted in partial reversal of the effect of emetine. These results suggest that newly synthesized class I MHC molecules are required for the generation of antigens recognized by anti-VSV CTL. 相似文献
55.
The effect of platelet activating factor on ovulation. 总被引:2,自引:0,他引:2
The mechanism of ovulation has been compared to an inflammatory reaction. Platelet activating factor (PAF) is an important mediator of inflammation as it may induce the production of prostaglandins and lysosomal enzyme. We evaluated the potential role of PAF in PMSG-HCG induced ovulation using CV3988, a specific PAF receptor antagonist in a superovulated ICR mice (9-12 weeks old). CV3988 blocked the ovulation in a dose dependent manner, and the significant reduced ovulatory efficiency was observed at more than 500 micrograms dose (p less than 0.001). The ovulatory efficiency reduced by CV3988 was reversed by PAF in a dose dependent manner. In vitro fertilization (IVF) rate of follicular oocytes with treatment of CV3988 was not different from that of ovulated ova without treatment. These results suggest that PAF may be involved in the ovulation process but the presence of PAF may not be essential for the fertilization of the ova as IVF. 相似文献
56.
Oxidation of dimethyl sulfide byPseudomonas acidovorans DMR-11 isolated from peat biofilter 总被引:1,自引:0,他引:1
Summary
Pseudomonas acidovorans DMR-11, capable of oxidizing dimethyl sulfide (DMS), was isolated from peat biofilter. DMS as a sole carbon or energy source was not degraded, but it was co-degraded in the medium containing organic carbon sources. The removal rate of DMS in heat-treated glucose medium was 1.12×10–17 mole/h cell at 30 °C. Dimethyl sulfoxide (DMSO) was the only product of DMS oxidation and was formed stoichiometrically. DMS was reversibly evolved in excess of DMSO. The cell free extract of strain DMR-11 oxidized DMS in presence of NADPH. 相似文献
57.
Hydrolysis of [Leu]- and [Met]enkephalin was determined in whole rat plasma in vitro by using HPLC-ECD to measure Tyr, Tyr-Gly and Tyr-Gly-Gly formation. Although [Leu]- and [Met]enkephalin did not differ in Tyr or Tyr-Gly accumulation, the amount of Tyr-Gly-Gly resulting from [Met]enkephalin hydrolysis was greater than that resulting from [Leu]enkephalin hydrolysis, and [Met]enkephalin's half-life in plasma was slightly shorter than that of [Leu]enkephalin. By comparing metabolite formation in the presence and absence of peptidase inhibitors with high selectivity for their respective enzymes, these studies demonstrated that aminopeptidase M and angiotensin converting enzyme are the major peptidases that hydrolyze enkephalins in rat plasma. 相似文献
58.
ATP-dependent interactions between myosin and actin in the lower eukaryote, Physarum polycephalum, are inhibited by micromolar levels of Ca2+. This inhibition is mediated by the binding of Ca2+ to myosin, the phosphorylation of which is required if Ca2+ is to inhibit the activities of myosin (Kohama, K., Trends Pharmacol. Sci. 11, 433-435 (1990)). As the first step to examine whether Ca2+ also regulates phosphorylation in the actomyosin system, we purified myosin light chain kinase (MLCK) of 55 kDa almost to homogeneity. The MLCK activity was high whether or not Ca2+ was present. However, a Ca(2+)-dependent inhibitory factor (CIF) purified from Physarum (Okagaki et al., Biochem. Biophys. Res. Commun. 176, 564-570 (1991)) was shown to reduce the MLCK activity in a Ca(2+)-dependent manner. Using crude preparations, not only MLCK but also myosin heavy chain kinase and actin kinase were shown to be inhibited by Ca2+ half-maximally at micromolar levels. Since CIF is the only Ca(2+)-binding protein in the preparations, we propose that this inhibitory Ca(2+)-regulation of the kinases for actomyosin is mediated by CIF. 相似文献
59.
A leptomycin B resistance gene of Schizosaccharomyces pombe encodes a protein similar to the mammalian P-glycoproteins 总被引:4,自引:0,他引:4
Kazunori Nishi Minoru Yoshida Marie Nishimura Mitsuo Nishikawa Makoto Nishiyama Sueharu Horinouchi Teruhiko Beppu 《Molecular microbiology》1992,6(6):761-769
Screening for leptomycin B (LMB)-resistant transformants in a gene library constructed in Schizosaccharomyces pombe with the chromosomal DNA of an LMB-resistant mutant of S. pombe and with multicopy plasmid pDB248' as the vector led to the isolation of a gene, named pmd1+, encoding a 1362-amino-acid protein. This protein showed great similarity in amino acid sequence to the mammalian P-glycoprotein encoded by the multidrug resistance gene, mdr, and the Saccharomyces cerevisiae a-factor transporter encoded by STE6. In addition, computer analyses predicted that the protein encoded by pmd1+ formed an intramolecular duplicated structure and each of the halves contained six transmembrane regions as well as two ATP-binding domains, as observed with the P-glycoproteins and the STE6 product. Consistent with this was that S. pombe cells containing the pmd1+ gene on a multicopy plasmid showed resistance not only to LMB but also to several cytotoxic agents. The pmd1 null mutants derived by gene disruption were viable and hypersensitive to these agents. All these data suggest that the pmd1+ gene encodes a protein that is a structural and functional counterpart of mammalian mdr proteins. 相似文献
60.
The relationship between paracoccidioidomycosis in ddY mouse and its estrous cycle was studied. Adult ddY mice of both sexes were used as experimental animals. Estrous cycle of female mice was examined before inoculation of Paracoccidioides brasiliensis yeast cells and mice were divided into 5 groups such as proestrus, estrus, metestrus-I, metestrus-II and diestrus. Each mouse was inoculated intravenously with 106
P. brasiliensis yeast cell units and sacrificed on day 28 after inoculation. Their internal organs were cultured, and in addition, their histopathologies were studied. As a result, there was no difference in the organ cultures among the male and the female mice of 5 groups. However, histopathologically, the female groups at estrus, metestrus-I and metestrus-II were affected more severely than the male group, and the susceptibility of the female mice to the fungus was closely related to their estrous cycles.Abbreviations BHI-D
brain heart infusion agar supplemented with 1.0% of anhydrous dextrose
- PAS
periodic acid-Schiff techniques
- PBS
phosphate buffered saline solution
- SD
standard deviation 相似文献