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1.
P. Katapodis A. Kavarnou S. Kintzios E. Pistola D. Kekos B.J. Macris P. Christakopoulos 《Biotechnology letters》2002,24(17):1413-1416
Neutral and acidic oligosaccharides were obtained from birchwood xylan by treatment with an endoxylanase, family 10 class, from Thermoascus aurantiacus. The main acidic xylooligosaccharide (aldotetrauronic acid) was separated from the hydrolysate by anion-exchange and size-exclusion chromatography and the primary structure was determined by 13C NMR spectroscopy. The aldotetrauronic yield was 15% (w/w) of the total solubilised sugars. The addition of purified aldoterauronic acid at 1.6–16 mg l–1 growth medium, induced callus and somatic embryogenesis in culture explants of common mallow (Malva silvestris L.) and cotton (Gosssypium hirsutum). 相似文献
2.
Abstract A mutant strain of Schizosaccharomyces pombe lacking dipeptidyl aminopeptidase yspI was isolated from a strain already defective in aminopeptidase activity by means of a staining technique with the chromogenic substrate ala-pro-4-methoxy-β-naphthylamide to screen colonies for the absence of the enzyme. The defect segregated 2+ :2− in meiotic tetrads, indicating a single chromosomal gene mutation, which was shown to be recessive. Gene dosage experiments indicated that the mutation resides in the structural gene of dipeptidyl aminopeptidase yspI, dpa 1+ . The dpa 1+ gene was located on chromosome III by using l m- fluorophen-ylalanine-induced haploidization and mitotic analysis. dpa1 mutants did not show any obvious phenotype under a variety of conditions tested. 相似文献
3.
4.
F. Kato T. Hino A. Nakaji M. Tanaka Y. Koyama 《Molecular & general genetics : MGG》1995,247(3):387-390
In many species of actinomycetes, carotenogenesis can be photoinduced. The capacity to respond to photoinduction is, however unstable and, in various strains of Streptomyces, is lost at a relatively high frequency. In Streptomyces setonii ISP5395, which normally produces no carotenoids, carotenoid-producing mutants can be obtained following protoplast regeneration. We report here the characterization of a gene, crtS, which was isolated from one such mutant and can confer on wild-type S. setonii ISP5395 cells the capacity to synthesize carotenoids. Sequence analysis of crtS reveals an open reading frame, which shows homology to genes that encode alternative sigma factors in Bacillus subtilis. We propose that crtS encodes a sigma factor which is necessary for the expression of a cryptic gene(s) for carotenoid biosynthesis in S. setonii ISP5395. 相似文献
5.
6.
V. G. Borkhvardt 《Russian Journal of Developmental Biology》2000,31(3):154-161
The development of the fin and limb buds involves a balance of centrifugal (active) and centripetal (passive) mechanical forces,
the first of which acts to move the walls of these structures away from each other and the second of which holds them together.
When the volume of the mesodermal core increases, the generated force meets with the resistance of the basal membrane, and
as a result, the limb bud has a tendency to acquire a cylindrical shape. Collagen fibers, individual mesenchymal cells, and
their groups hold together the dorsal and the ventral wall of the limb bud, prevent the movement of these walls away from
each other, and in this way direct bud growth along the proximodistal and the anteroposterior axes. The balance of the forces
which stretch the ectodermal layer and those which constrain it has also been observed in the development of other body parts. 相似文献
7.
《Journal of molecular biology》2021,433(19):167156
Na+/H+ antiporters comprise a super-family (CPA) of membrane proteins that are found in all kingdoms of life and are essential in cellular homeostasis of pH, Na+ and volume. Their activity is strictly dependent on pH, a property that underpins their role in pH homeostasis. While several human homologues have long been drug targets, NhaA of Escherichia coli has become the paradigm for this class of secondary active transporters as NhaA crystal structure provided insight into the architecture of this molecular machine. However, the mechanism of the strict pH dependence of NhaA is missing. Here, as a follow up of a recent evolutionary analysis that identified a ‘CPA motif’, we rationally designed three E. coli NhaA mutants: D133S, I134T, and the double mutant D133S-I134T. Exploring growth phenotype, transport activity and Li+-binding of the mutants, we revealed that Asp133 does not participate directly in proton binding, nor does it directly dictate the pH-dependent transport of NhaA. Strikingly, the variant I134T lost some of the pH control, and the D133S-Il134T double mutant retained Li+ binding in a pH independent fashion. Concurrent to loss of pH control, these mutants bound Li+ more strongly than the WT. Both positions are in close vicinity to the ion-binding site of the antiporter, attributing the results to electrostatic interaction between these residues and Asp164 of the ion-binding site. This is consistent with pH sensing resulting from direct coupling between cation binding and deprotonation in Asp164, which applies also to other CPA antiporters that are involved in human diseases. 相似文献
8.
Concentration factor and biological half-life of 54Mn were determined in three species representing an ecologically and economically important food chain. Green algae (Chlorella spp.), Daphnia magna and yellow perch (Perca flavescens) were exposed to 54Mn in water and assayed for 54Mn uptake. Steady state concentration factors computed from the laboratory data for algae, Daphnia and perch were 4230, 17 000 and 11, respectively. Respective biological half-lives were 1.6, 1.2 and 8.3 days. 相似文献
9.
K.S. Misono R.T. Grammer H. Fukumi T. Inagami 《Biochemical and biophysical research communications》1984,123(2):444-451
Four peptides possessing both natriuretic activity and smooth muscle relaxant activity were isolated from rat atrium and their amino acid sequences determined. The four peptides designated ANF-I, ANF-II, ANF-III and ANF-IV containing 35, 31, 30 and 25 amino acid residues, respectively, were obtained in a molar ratio of 4:60:20:16. The predominant species ANF-II, which may represent the native form of ANF, has the following sequence: (H2N)-G-P-R-S-L-R-R-S-S-C-F-G-G-R-I-D-R-I-G-A-Q-S-G-L-G-C-N-S-F-R-Y-(COOH) in which Cys-10 and Cys-26 are disulfide linked. Cleavage of the aspartyl linkage at position 16 by staphylococcal protease caused complete inactivation, indicating that the ring conformation is essential. The dose-response relationships determined for the four pepdides in relaxing norepinephrine-induced contraction of rabbit thoracic aorta showed half-maximum relaxation at concentrations ranging from 1.5 × 10?9 to 2.5 × 10?9 M. Comparable dose-response relationships were observed in relaxation of carbacol-induced contraction of chick rectum strips as tested with ANF-II and ANF-IV. 相似文献
10.
The association between the red macroalga Jania adhaerens J. V. Lamour. and the sponge Haliclona caerulea is the most successful life‐form between 2 and 4 m depth in Mazatlán Bay (Mexican Pacific). J. adhaerens colonizes the rocky intertidal area and penetrates into deeper areas only when it lives in association with H. caerulea. The aposymbiotic form of the sponge has not been reported in the bay. To understand the ecological success of this association, we examined the capacity of J. adhaerens to acclimate in Mazatlán Bay using transplant experiments. The transplanted aposymbiotic J. adhaerens did not survive the first 2 weeks; however, J. adhaerens when living in association with H. caerulea, acclimated easily to depth, showing no sign of mortality during the 103 d of the experiment. We conclude that the ability of J. adhaerens to colonize in deeper areas in this hydrodynamic environment may in part rely on the protection provided by the sponge to the algal canopy. Both species contribute to the shape of the associated form. Nevertheless, the morphological variation in the association appears to be dominated by the variation in J. adhaerens canopy to regulate pigment self‐shading under light‐limited conditions and/or tissue resistance under high hydrodynamics. Consequently, our results are consistent with light as the abiotic controlling factor, which regulates the lower depth distribution of the association in Mazatlán Bay, through limiting the growth rate of J. adhaerens. Hydrodynamics may determine the upper limit of the association by imposing high mass losses. 相似文献