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Large, rapidly evolving intergenic spacers in the mitochondrial DNA of the salamander family Ambystomatidae (Amphibia: Caudata) 总被引:5,自引:2,他引:3
We report the presence, in the mitochondrial DNA (mtDNA) of all of the
sexual species of the salamander family Ambystomatidae, of a shared 240- bp
intergenic spacer between tRNAThr and tRNAPro. We place the intergenic
spacer in context by presenting the sequence of 1,746 bp of mtDNA from
Ambystoma tigrinum tigrinum, describe the nucleotide composition of the
intergenic spacer in all of the species of Ambystomatidae, and compare it
to other coding and noncoding regions of Ambystoma and several other
vertebrate mtDNAs. The nucleotide substitution rate of the intergenic
spacer is approximately three times faster than the substitution rate of
the control region, as shown by comparisons among six Ambystoma
macrodactylum sequences and eight members of the Ambystoma tigrinum
complex. We also found additional inserts within the intergenic spacers of
five species that varied from 87-444 bp in length. The presence of the
intergenic spacer in all sexual species of Ambystomatidae suggests that it
arose at least 20 MYA and has been a stable component of the ambystomatid
mtDNA ever since. As such, it represents one of the few examples of a large
and persistent intergenic spacer in the mtDNA of any vertebrate clade.
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Hlima HB Aghajari N Ali MB Haser R Bejar S 《Journal of industrial microbiology & biotechnology》2012,39(4):537-546
The role of two amino acid residues linked to the two catalytic histidines His54 and His220 in kinetics and physicochemical
properties of the Streptomyces sp. SK glucose isomerase (SKGI) was investigated by site-directed mutagenesis and molecular modeling. Two single mutations,
F53L and G219D, and a double mutation F53L/G219D was introduced into the xylA SKGI gene. The F53L mutation increases the thermostability and the catalytic efficiency and also slightly shifts the optimum
pH from 6.5 to 7, but displays a profile being similar to that of the wild-type enzyme concerning the effect of various metal
ions. The G219D mutant is resistant to calcium inhibition retaining about 80% of its residual activity in 10 mM Ca2+ instead of 10% for the wild-type. This variant is activated by Mn2+ ions, but not Co2+, as seen for the wild-type enzyme. It does not require the latter for its thermostability, but has its half-life time displaced
from 50 to 20 min at 85°C. The double mutation F53L/G219D restores the thermostability as seen for the wild-type enzyme while
maintaining the resistance to the calcium inhibition. Molecular modeling suggests that the increase in thermostability is
due to new hydrophobic interactions stabilizing α2 helix and that the resistance to calcium inhibition is a result of narrowing
the binding site of catalytic ion. 相似文献
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A simple, fast and sensitive method was developed to verify the presence of
the sialyl Lewis(x) antigen on an N-linked glycoprotein. High performance
liquid chromatography-electrospray mass spectrometry (HPLC-ESI/MS) was used
to identify which of the five N-linked glycosylation sites of human plasma
alpha1-acid-glycoprotein (orosomucoid, OMD) contain the sialyl Lewis(x)
antigen. OMD was digested with proteolytic enzymes and analyzed by reversed
phase chromatography coupled with on-line ESI/MS. A tandem mass
spectrometry experiment was designed to detect the presence of the sialyl
Lewis(x) antigen based on the observation of an 803 mass to charge ratio (
m/z ) ion produced in the intermediate pressure region of the ESI
interface. The ESI/MS signal at m/z 803 is consistent with an oxonium ion
for a glycan structure containing NeuAc, Gal, GlcNAc, and Fuc. The identity
of the m/z 803 ion was confirmed by ESI/MS/MS analysis of the m/z 803
fragment ion and comparison with a sialyl Lewis(x) standard. The
stereochemistry and linkage positions were assigned using previous NMR
analysis but could be determined with permethylation analysis if necessary.
The analysis of OMD gave a pattern showing signal for the sialyl Lewis(x)
antigen coeluting with each of the five N-linked glycopeptides. The ability
to monitor sialyl Lewis(x) expression at each of the five sites is of
interest in the study of OMD's role in inflammatory diseases.
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Survival of vegetation on soil-capped mining wastes is often impaired during dry seasons due to the limited amount of water stored in the shallow soil capping. Growth and survival of Rhodes grass (Chloris gayana) during soil drying on various layered capping sequences constructed of combinations of topsoil, subsoil, seawater-neutralised residue sand and low grade bauxite was determined in a glasshouse. The aim was to describe the survival of Rhodes grass in terms of plant and soil water relationships. The soil water characteristic curve and soil texture analysis was a good predictor of plant survival. The combination of soil with a high water holding capacity and low soil water diffusivity (e.g. subsoil with high clay contents) with soil having a high water holding capacity and high diffusivity (e.g. residue sand) gave best survival during drying down (up to 88 days without water), whereas topsoil and low grade bauxite were unsuitable (plants died within 18–39 days). Clayey soil improved plant survival by triggering a water stress response during peak evaporative water demand once residue sand dried down and its diffusivity fell below a critical range. Thus, for revegetation in seasonally dry climates, soil capping should combine one soil with low diffusivity and one or more soils with high total water holding capacity and high diffusivity. 相似文献
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Sameh Ben Mabrouk Dorra Ayadi-Zouari Hajer Ben Hlima Samir Bejar 《Journal of industrial microbiology & biotechnology》2013,40(9):947-953
Maltogenic amylase from Bacillus sp. US149 (MAUS149) is a cyclodextrin (CD)-degrading enzyme with a high preference for CDs over maltooligosaccharides. In this study, we investigated the roles of residue Asp46 in the specificity and catalytic properties of MAUS149 by using site-directed mutagenesis. Three mutated enzymes (D46V, D46G and D46N) were constructed and studied. The three mutants were found to be similar to the wild-type MAUS149 regarding thermoactivity, thermostability and pH profile. Nevertheless, the kinetic parameters for all the substrates of the mutant enzymes D46V and D46G were altered enormously as compared with those of the wild type. Indeed, the K m values of MAUS149/D46G for all substrates were strongly increased. Nevertheless, the affinity and catalytic efficiency of MAUS149/D46V toward β-CD were increased fivefold as compared with those of MAUS149. Molecular modelling suggests that residue D46 forms a salt bridge with residue K282. This bond would maintain the arrangement of side chains of residues Y45 and W47 in a particular orientation that promotes access to the catalytic site and maintains the substrate therein. Hence, any replacement with uncharged amino acids influenced the flexibility of the gate wall at the substrate binding cleft resulting in changes in substrate selectivity. 相似文献
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Nadia Zara? Jaouadi Bassem Jaouadi Hajer Ben Hlima Hatem Rekik Mouna Belhoul Maher Hmidi Houda Slimene Ben Aicha Chiraz Gorgi Hila Abdessatar Toumi Nushin Aghajari Samir Bejar 《PloS one》2014,9(9)
The sapB gene, encoding Bacillus pumilus CBS protease, and seven mutated genes (sapB-L31I, sapB-T33S, sapB-N99Y, sapB-L31I/T33S, sapB-L31I/N99Y, sapB-T33S/N99Y, and sapB-L31I/T33S/N99Y) were overexpressed in protease-deficient Bacillus subtilis DB430 and purified to homogeneity. SAPB-N99Y and rSAPB displayed the highest levels of keratinolytic activity, hydrolysis efficiency, and enzymatic depilation. Interestingly, and at the semi-industrial scale, rSAPB efficiently removed the hair of goat hides within a short time interval of 8 h, thus offering a promising opportunity for the attainment of a lime and sulphide-free depilation process. The efficacy of the process was supported by submitting depilated pelts and dyed crusts to scanning electron microscopic analysis, and the results showed well opened fibre bundles and no apparent damage to the collagen layer. The findings also revealed better physico-chemical properties and less effluent loads, which further confirmed the potential candidacy of the rSAPB enzyme for application in the leather industry to attain an ecofriendly process of animal hide depilation. More interestingly, the findings on the substrate specificity and kinetic properties of the enzyme using the synthetic peptide para-nitroanilide revealed strong preferences for an aliphatic amino-acid (valine) at position P1 for keratinases and an aromatic amino-acid (phenylalanine) at positions P1/P4 for subtilisins. Molecular modeling suggested the potential involvement of a Leu31 residue in a network of hydrophobic interactions, which could have shaped the S4 substrate binding site. The latter could be enlarged by mutating L31I, fitting more easily in position P4 than a phenylalanine residue. The molecular modeling of SAPB-T33S showed a potential S2 subside widening by a T33S mutation, thus suggesting its importance in substrate specificity. 相似文献
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Osorio-Córdoba J LL Rodriguez-Verástegui F Díaz de León-Sánchez E Bosquez-Molina JR Verde-Calvo HB Escalona-Buendía LJ Pérez-F lores C Pelayo-Zaldívar 《Phyton》2015,84(2):375-384
Cactus stems, the cladodes of Opuntia spp. cacti, are consumed in Mexico and other countries due to their fresh and herbaceous flavor, and because of their widely known nutraceutical benefits. In order to extend the postharvest life of this vegetable, the effect of a modified atmosphere packaging (MAP) was studied in cactus stems of the cultivar Atlixco stored at 4 ± 1 °C for 20 days under three types of atmospheres: (1) air (passive atmosphere), (2) 5 kPa O2 + 4 kPa CO2, and (3) N2. During storage, the titratable acidity decreased and the color of cladodes became darker and less green; however, the 5 kPa O2 + 4 kPa CO2 atmosphere was able to preserve both quality characteristics. All modified atmospheres reduced weight loss (from 8 to <2%) and the symptoms of chilling injury, and this physiological disorder appeared earlier in controls than in MAP-stored cladodes. The levels of fermentation metabolites were low in all three evaluated atmospheres. Because of this, only cladodes stored under the N2 atmosphere were selected for furthersensory analysis of the MAP effect on odor perception as evaluated by a trained panel. Results indicated that there was no detrimental effect (atypical odors) of MAP on this sensory characteristic. We conclude that cultivar Atlixco is suitable for preservation using MAP technology. 相似文献
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A Jain M Sundriyal S Roshnibala R Kotoky PB Kanjilal HB Singh RC Sundriyal 《Journal of ethnobiology and ethnomedicine》2011,7(1):29