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101.
The extracellular β-agarase LSL-1 produced by an agar-liquefying, soil bacterium Acinetobacter sp., AG LSL-1 was purified to homogeneity by combination of ion-exchange and size exclusion chromatography with final yield of 44%. The enzyme has a specific activity of 397 U mg−1 protein and with a molecular mass of 100 kDa. The agarase was active in the pH range of 5.0–9.0, optimally at pH 6.0 and temperature between 25 °C and 55 °C and optimal at 40 °C. The enzyme retained 63% of native activity at 50 °C suggesting it is a thermostable. The activity of the agarase was completely inhibited by metal ions, Hg2+, Ag+ and Cu2+, whereas 25–40% of native activity was retained in the presence of Zn2+, Sn2+ and SDS. Neoagarobiose was the final product of hydrolysis of both agarose and neoagarohexaose by the purified agarase LSL-1. Based on the molecular mass and final products of agarose hydrolysis, the β-agarase LSL-1 may be further grouped under group III β-agarases and may be a member of GH-50 family. This is the first report on the purification and biochemical characterization of β-agarase from an agar-liquefying Acinetobacter species. 相似文献
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103.
Disulphide bridges involving juxtaposed half-cystines are observed in a number of protein three-dimensional structures analyzed from the Protein Data Bank. These disulphide bridges comprise a 'ring of 8-atoms' corresponding to Calpha1-C'-N-Calpha2-Cbeta2-Sgamma2-Sgamma1-Cbeta1-Calpha1 in the two half-cystines. The presence of such disulphide bridges introduces a 'bend' or 'kink' in the protein polypeptide chain. 相似文献
104.
Summary. Our observations on the growth stimulatory nature of mimosine, (β-(3-hydroxy-4-pyridon-1-yl)-L-alanine), the toxic non-protein
plant amino acid, in some model experimental systems, warranted sensitive and selective routine estimations. For the determination
of both mimosine and DHP, an indirect spectrophotometric method was developed based on their individual reaction with known
excess of DZSAM and by estimating the remaining DZSAM with N-(1-naphthyl)ethylene-diamine (NEDA). The resultant decrease in
the secondary coupled product was measured at 540 nm. On equimolar basis, DHP had 40% of the reactivity of mimosine while
interference from other relevant compounds was 15–35%. The determination of mimosine and DHP in tissue samples under different
physiological conditions was effected after paper chromatographic separation of mimosine and DHP with distinctly differing
Rf, from other compounds. The indirect method is superior in terms of absolute selectivity, sensitivity and ease of applicability
with linear decreases in absorbance, proportional to increasing concentrations of mimosine from 0.1 to 0.75 μM or DHP from
0.2 to 1.5 μM and with recoveries of 99.2 to 100.5%. 相似文献
105.
Microevolution of cytochrome bd oxidase in Staphylococci and its implication in resistance to respiratory toxins released by Pseudomonas
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Voggu L Schlag S Biswas R Rosenstein R Rausch C Götz F 《Journal of bacteriology》2006,188(23):8079-8086
Pseudomonas aeruginosa and Staphylococcus aureus are opportunistic pathogens and frequently coinfect the lungs of cystic fibrosis patients. P. aeruginosa secretes an arsenal of small respiratory inhibitors, like pyocyanin, hydrogen cyanide, or quinoline N-oxides, that may act against the commensal flora as well as host cells. Here, we show that with respect to their susceptibility to these respiratory inhibitors, staphylococcal species can be divided into two groups: the sensitive group, comprised of pathogenic species such as S. aureus and S. epidermidis, and the resistant group, represented by nonpathogenic species such as S. carnosus, S. piscifermentans, and S. gallinarum. The resistance in the latter group of species was due to cydAB genes that encode a pyocyanin- and cyanide-insensitive cytochrome bd quinol oxidase. By exchanging cydB in S. aureus with the S. carnosus-specific cydB, we could demonstrate that CydB determines resistance. The resistant or sensitive phenotype was based on structural alterations in CydB, which is part of CydAB, the cytochrome bd quinol oxidase. CydB represents a prime example of both microevolution and the asymmetric pattern of evolutionary change. 相似文献
106.
Transient expression of adenoviral oncoprotein E1B55K in normal cells induces aggresome formation and sequestration of critical host proteins in aggresomes. Our previous studies reported that Sequence Specific Binding Protein 2 (SSBP2), a candidate tumor suppressor is recruited to aggresomes in adenovirally transformed human embryonal kidney 293 (HEK293) cells. To understand the extent and significance of the E1B55K-SSBP2 interactions in these cells, we have examined SSBP2 localization under conditions of stress in HEK293 cells. SSBP2 localizes to PML- Nuclear Bodies (PML-NBs) in response to inhibition of nuclear export, treatment with etoposide, hydroxyurea or gamma irradiation only in HEK293 cells. Furthermore, the PML-NBs grow in size and number in response to radiation over a 24 hour period in HEK293 cells analogous to previous findings for other cell types. Nonetheless, we conclude that E1B55K subverts SSBP2 function in HEK293 cells. These findings demonstrate the limitations in using HEK293 cells to study DNA damage response and other cellular processes since SSBP2 and similar regulatory proteins are aberrantly localized due to constitutive E1B55K expression. 相似文献
107.
BCR-ABL kinase domain inhibition can be used to treat chronic myeloid leukemia. The inhibitors such as imatinib, dasatinib and nilotinib are effective drugs but are resistant to some BCR-ABL mutations. The pan-BCR-ABL kinase inhibitor ponatinib exhibits potent activity against native, T315I, and all other clinically relevant mutants, and showed better inhibition than the previously known inhibitors. We have studied the molecular dynamics simulations and calculated solvated interaction energies of native and fourteen mutant BCR-ABL kinases (M244V, G250E, Q252H, Y253F, Y253H, E255K, E255V, T315A, T315I, F317L, F317V, M351T, F359V and H396P) complexed with ponatinib. These studies revealed that the interactions between ponatinib and individual residues in BCR-ABL kinase are also affected due to the remote residue mutations. We report that some residues, Met244, Lys245, Gln252, Gly254, Leu370 and Leu298 do not undergo any conformational changes, while the fluctuations in residues from P-loop, β3-, β5- strands and αC- helix are mainly responsible for ponatinib binding to native and all mutant BCR-ABL kinases. Our work provides the molecular mechanisms of native and mutant BCR-ABL kinases inhibition by ponatinib at atomic level that has not been studied before. 相似文献
108.
Sanjoy Das Kuttanappilly Velayudhanelayadom Lalitha Nirmala Thampuran Poothavallil Kumaran Surendran 《Annals of microbiology》2013,63(3):1093-1098
Listeria monocytogenes, which is an intracellular pathogen, causes various illnesses in human as well as in animals. The pathogenicity of this organism depends upon the presence of different virulence genes. A total of 324 tropical seafood and fishery environmental samples were screened for L. monocytogenes. The incidence of the human pathogenic species L. monocytogenes was 1.2 % of the samples. Listeria spp. was detected in 32.3, 27.1, and 5 % of fresh, frozen, and dry fish samples, respectively. Listeria innocua was found to be the most prevalent species of Listeria in the tropical seafood and environmental samples of Kerala. Listeria monocytogenes and L. innocua isolates were confirmed by multiplex PCR. L. monocytogenes isolates from the four positive samples showed phosphatidylinositol-specific phospholipase C reaction on Chromocult® Listeria selective agar. Molecular characterization of L. monocytogenes isolates for virulence genes revealed the presence of β-hemolysin (hly), plcA, actA, metalloprotease (mpl), iap and prfA genes in all the isolates recovered from the positive samples. 相似文献
109.
110.
Peter B. Madrid Sidharth Chopra Ian D. Manger Lynne Gilfillan Tiffany R. Keepers Amy C. Shurtleff Carol E. Green Lalitha V. Iyer Holli Hutcheson Dilks Robert A. Davey Andrey A. Kolokoltsov Ricardo Carrion Jr Jean L. Patterson Sina Bavari Rekha G. Panchal Travis K. Warren Jay B. Wells Walter H. Moos RaeLyn L. Burke Mary J. Tanga 《PloS one》2013,8(4)