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121.
Expression of human asparagine synthetase in Escherichia coli 总被引:4,自引:0,他引:4
Human asparagine synthetase was expressed in Escherichia coli. Synthesis of the enzyme was demonstrated by immunoblotting and by complementation of asparagine auxotrophy in E. coli. The recombinant enzyme was shown to have both the ammonia- and glutamine-dependent asparagine synthetase activity in vitro. Compared to asparagine synthetase isolated from beef pancreas, the one expressed in E. coli migrated at a slightly slower rate on a denaturing protein gel. In contrast with previous reports, the data obtained here strongly suggest that the active enzyme is a homodimer. The production of soluble and active enzyme was shown to be highly temperature-dependent. Expression at 37 degrees C yielded no soluble enzyme, whereas growth at 30 and 21 degrees C favored the production of soluble asparagine synthetase. The incubation temperature was also important for complementation of asparagine auxotrophy in E. coli, as growth in the absence of asparagine occurred at 30 degrees C and not at 37 degrees C. 相似文献
122.
K Vancompernolle M Gimona M Herzog J Van Damme J Vandekerckhove V Small 《FEBS letters》1990,274(1-2):146-150
Limited chymotryptic cleavage of turkey gizzard calponin yields a 13 kDa fragment which could be purified by its ability to bind to Sepharose-immobilized tropomyosin. This 13 kD polypeptide is shown to be derived from a 22 kDa fragment. Complete amino acid sequence analysis of the 13 kD and 22 kD fragments reveals high homology with the formerly characterized smooth muscle-specific protein SM22 alpha (Pearlstone, J.R., Weber, M., Lees-Miller, J.P., Carpenter, M.R. and Smillie L.B., 1987, J. Biol. Chem. 262, 5985-5991) and the product of gene mp20 of Drosophila (Ayme-Southqate, A., Lasko, P., French, C, and Pardue, M.L. [(1989) J. Cell Biol. 108, 521-531]. Futhermore we recognize sequence elements of a putative actin-binding domain of alpha-actinin, the calpactin I or p 36 sequence, and a consensus motif present in the repeats of the gene product of the candidate unc-87 gene of C. elegans (S.D. Goetinck and R.H. Waterston, personal communication). 相似文献
123.
Laid Douidah Lieven De Zutter Filip Van Nieuwerburgh Dieter Deforce Hanne Ingmer Olivier Vandenberg Anne-Marie Van den Abeele Kurt Houf 《PloS one》2014,9(1)
In this study, we report the screening of four Arcobacter species for the presence of small and large plasmids. Plasmids were present in 9.9% of the 273 examined strains. One Arcobacter cryaerophilus and four Arcobacter butzleri plasmids were selected for further sequencing. The size of three small plasmids isolated from A. butzleri and the one from A. cryaerophilus strains ranged between 4.8 and 5.1 kb, and the size of the large plasmid, isolated from A. butzleri, was 27.4 kbp. The G+C content of all plasmids ranged between 25.4% and 26.2%. A total of 95% of the large plasmid sequence represents coding information, which contrasts to the 20 to 30% for the small plasmids. Some of the open reading frames showed a high homology to putative conserved domains found in other related organisms, such as replication, mobilization and genes involved in type IV secretion system. The large plasmid carried 35 coding sequences, including seven genes in a contiguous region of 11.6 kbp that encodes an orthologous type IV secretion system found in the Wolinella succinogenes genome, Helicobacter pylori and Campylobacter jejuni plasmids, which makes this plasmid interesting for further exploration. 相似文献
124.
Heterologous gene expression in Lactococcus lactis subsp. lactis: synthesis, secretion, and processing of the Bacillus subtilis neutral protease 总被引:1,自引:0,他引:1
M van de Guchte J Kodde J M van der Vossen J Kok G Venema 《Applied and environmental microbiology》1990,56(9):2606-2611
The Bacillus subtilis nprE gene lacking its own promoter sequence was inserted in the lactococcal expression vector pMG36e. Upon introduction of the recombinant plasmid into Lactococcus lactis subsp. lactis strain MG1363, neutral protease activity could be visualized by the appearance of large clearing zones around colonies grown on milk agar plates. By measuring the activities of the neutral protease and the intracellular enzyme lactate dehydrogenase in culture supernatants and cell fractions, it was demonstrated that the neutral protease was actively secreted into the growth medium. This was corroborated by using the Western blot (immunoblot) technique, which showed the presence of the mature form of the neutral protease in the culture supernatant. On the basis of these results, it is concluded that the B. subtilis neutral protease gene was expressed in L. lactis and that the gene product was secreted into the growth medium and was apparently correctly processed to produced a biologically active protein. The secretion of this particular enzyme may be helpful in achieving accelerated cheese ripening. 相似文献
125.
Evelien Wynendaele Frederick Verbeke Sofie Stalmans Bert Gevaert Yorick Janssens Christophe Van De Wiele Kathelijne Peremans Christian Burvenich Bart De Spiegeleer 《PloS one》2015,10(11)
Bacteria communicate with each other by the use of signaling molecules, a process called ‘quorum sensing’. One group of quorum sensing molecules includes the oligopeptides, which are mainly produced by Gram-positive bacteria. Recently, these quorum sensing peptides were found to biologically influence mammalian cells, promoting i.a. metastasis of cancer cells. Moreover, it was found that bacteria can influence different central nervous system related disorders as well, e.g. anxiety, depression and autism. Research currently focuses on the role of bacterial metabolites in this bacteria-brain interaction, with the role of the quorum sensing peptides not yet known. Here, three chemically diverse quorum sensing peptides were investigated for their brain influx (multiple time regression technique) and efflux properties in an in vivo mouse model (ICR-CD-1) to determine blood-brain transfer properties: PhrCACET1 demonstrated comparatively a very high initial influx into the mouse brain (Kin = 20.87 μl/(g×min)), while brain penetrabilities of BIP-2 and PhrANTH2 were found to be low (Kin = 2.68 μl/(g×min)) and very low (Kin = 0.18 μl/(g×min)), respectively. All three quorum sensing peptides were metabolically stable in plasma (in vitro) during the experimental time frame and no significant brain efflux was observed. Initial tissue distribution data showed remarkably high liver accumulation of BIP-2 as well. Our results thus support the potential role of some quorum sensing peptides in different neurological disorders, thereby enlarging our knowledge about the microbiome-brain axis. 相似文献
126.
In order to model the interaction of hemin with DNA and other polynucleotides, we have studied the degradation of DNA, RNA, and polynucleotides of defined structure by [meso-tetrakis(N-methyl-4-pyridyl)porphinato]manganese(III) (MnTMPP) + KHSO5. The activated porphyrin was shown to release adenine, thymine, and cytosine from DNA; RNA degradation afforded adenine, uracil, and cytosine. The same products were obtained from single- and double-stranded DNA oligonucleotides of defined sequence, and also from single-stranded DNA and RNA homopolymers. The overall yield of bases from the dode-canucleotide d(CGCT3A3GCG) was equal to 14% of the nucleotides present initially, indicating that each porphyrin catalyzed the release of approximately 4 bases. Although no guanine was detected as a product from any of the substrates studied, the ability of MnTMPP + KHSO5 to degrade guanine nucleotides was verified by the destruction of pGp, and by the appearance of bands corresponding to guanosine cleavage following treatment of 32P end labeled DNA restriction fragments with activated MnTMPP. Inspection of a number of sites of MnTMPP-promoted cleavage indicated that the process was sequence-selective, occurring primarily at G residues that were part of 5'-TG-3' or 5'-AG-3' sequences, or at T residues. Also formed in much greater abundance were alkali-labile lesions; these were formed largely at guanosine residues. Also studied was the degradation of a 47-nucleotide RNA molecule containing two hairpins. Degradation of the 5'-32P end labeled RNA substrate afforded no distinct, individual bands, suggesting that multiple modes of degradation may be operative.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
127.
128.
129.
Herman van der Kooij Ron Jacobs Bart Koopman Henk Grootenboer 《Biological cybernetics》1999,80(5):299-308
A model is presented to study and quantify the contribution of all available sensory information to human standing based
on optimal estimation theory. In the model, delayed sensory information is integrated in such a way that a best estimate of
body orientation is obtained. The model approach agrees with the present theory of the goal of human balance control. The
model is not based on purely inverted pendulum body dynamics, but rather on a three-link segment model of a standing human
on a movable support base. In addition, the model is non-linear and explicitly addresses the problem of multisensory integration
and neural time delays. A predictive element is included in the controller to compensate for time delays, necessary to maintain
erect body orientation. Model results of sensory perturbations on total body sway closely resemble experimental results. Despite
internal and external perturbations, the controller is able to stabilise the model of an inherently unstable standing human
with neural time delays of 100 ms. It is concluded, that the model is capable of studying and quantifying multisensory integration
in human stance control. We aim to apply the model in (1) the design and development of prostheses and orthoses and (2) the
diagnosis of neurological balance disorders.
Received: 25 August 1997 / Accepted in revised form: 8 December 1998 相似文献
130.
Eva Decru Nathan Vranken Pedro H. N. Bragança Jos Snoeks Maarten Van Steenberge 《Journal of fish biology》2020,96(5):1186-1201
Based on literature, museum collections and three recent expeditions, an annotated species list of the Lake Edward, East Africa, drainage system is presented, excluding the endemic haplochromines. A total of 34 non-Haplochromis species belonging to 10 families and 21 genera are recorded from the system. Three of these are endemic and two others have been introduced in the region. Six species are new records for the Lake Edward system. A species accumulation curve indicates that we probably covered most of the non-Haplochromis species in the area sampled during the recent expeditions, but undetected species might still be present in the Congolese part of the system, which is poorly sampled. A comparison of the species list with those of neighbouring basins confirmed the placement of the Lake Edward system within the east-coast ichthyofaunal province. 相似文献