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1.
Using the crystal structure of allophycocyanin from cyanobacterium Spirulina platensis (APC-SP) as a search model,the crystal structure of allophycocyanin from red algae Porphyra yezoensis (APC-PY) has been studied by molecular replacement methods.The APC-PY crystals (Form 3) belong to the space group of R32,cell dimensions a=b= 10.53 nm,c=18.94 nm,α= β= 90°,γ=120°;there is one αβ monomer in each crystallographic asymmetric unit in the cell.The translation function search gave a unique peak with a correlation coefficient (Cc) of 67.0% and an R-factor of 36.1% for reflection data from 1.0 to 0.4 nm.Using the results by molecular replacement,the initial model of APC-PY was built,and the coincidence of the chromophore in APC-PY initial model with its 2Fo-Fc OMIT map further confirms the results by molecular replacement. 相似文献
2.
Summary. New bioinorganic complexes of the aspartic acid with the antimony or bismuth triiodide were synthesized by a direct solid–solid
reaction at room temperature. The formula of the complex is MI3[OOCCH2CH(NH2)CO]2.5 · 2.5H2O (M = Sb, Bi). The complex may be a dimer with bridge structure. The crystal structure of the complexes belongs to a triclinic
system. The lattice parameters are a = 0.9883 nm, b = 1.4284 nm, c = 2.0114 nm, α = 94.46°, β = 99.76° and γ = 100.1° for
the complex of antimony and a = 0.9756 nm, b = 1.4560 nm, c = 1.9875 nm, α = 94.18°, β = 97.25° and γ = 101.16° for the complex
of bismuth. The infrared spectra and thermal analyses can demonstrate the complex formation between the aspartic acid and
the antimony or bismuth ion. 相似文献
3.
BmK M4 is a neutral neurotoxin in the BmK toxin series. It is medially toxic and belongs to group III cc-toxins. The purified sample was crystallized in rhombic space group P6 Using an X-ray diffraction technique, the crystal structure of BmK M4 was revealed by molecular replacement at 0.20 nm resolution. The model was refined. The final crystallographic R factor was 0.142 and the free R factor was 0.173. The root mean square deviation is 0.001 5 nm for the bond length and 1.753° for the bond angles. 64 water molecules were added to the asymmetric unit. The refined structure showed an unusual non-prolyl cis peptide bond at residue 10. The structure was compared with group II a-toxin BmK M8 (an acidic, weak toxin). The potential structural implications of the cis peptide bond were discussed. 相似文献
4.
The selenium-containing phycocyanin from the selenium-rich algae (Spirulina platensis) has been crystallized in two crystal forms by the hanging-drop vapor diffusion techniques. A chromatographic procedure of gel filtration and anion exchange was used for purification. Form I crystal with space group P21 and cell parameters a =108.0 ?, b= 117.0 ?, c = 184.0?, β= 90.2° and 12(αβ) units in the asymmetric unit was obtained by using (NH4)2SO4 as precipitant. These crystals diffract up to 2.8 ?. Form II crystal obtained by using PEG4000 as precipitant belongs to space group P63 with unit cell constants a = 155.0 ?, c = 40.3 ?, γ =120.0° and one(αβ) unit in the asymmetric unit. The crystals diffract beyond 2.9 ?. The possible stacking forms of phycocyanin molecules in the first crystal form were discussed. 相似文献
5.
The F1-ATP synthase complex constitutes the catalytic component of F1F0-ATP synthase, the primary ATP synthetic enzyme in the cell. Previous studies indicate that the glacier ice worm, Mesenchytraeus solifugus, maintains unusually high ATP levels that continue to rise as temperatures decline, suggesting that molecular changes within
ice worm F1-ATP synthase subunits may contribute to this energetic anomaly. In this report, we compared ice worm F1-ATP synthase subunits (α, β, γ) with homologues across metazoan phyla (arthropod, chordate, nematode) and among a group of clitellate annelids (Enchytraeus albidus, Enchytraeus buchholzi, Lumbriculus variegatus, Theromyzon tessulatum). Amino acid alignments indicated that ice worm F1-ATP α and F1-ATP β subunits share strong sequence homology with their mesophilic counterparts, respectively, but that ATP γ has diverged more rapidly. Moreover, F1-ATP α and F1-ATP β displayed amino acid compositional changes consistent with trends observed in other cold adapted proteins, while F1-ATP γ diverged in unexpected directions (e.g., gains in size, charged residues). Several ice worm-specific amino acid substitutions
map to positions near the F1-ATP β catalytic site while others occur near subunit contact sites. 相似文献
6.
From a heterotrophic bacterium,Xanthomonas sp. DY44 which was previously reported to oxidize hydrogen sulfide (H2S) to polysulfide, cytochromec-555 (cyt.c-555) responsible for oxidation of sulfide was purified by DEAE-Toyopearl and Sepadex G-75 column chromatography. Cyt.c-555 with a molecular weight of 12,500 showed maximum absorption at 555 nm (α-peak), 522 nm (β-peak) and 417 nm (γ-peak) for
the reduced form which was prepared by addition of Na2S2O4. Cyt.c-555 was also reduced by addition of sulfide (Na2S and H2S), and the oxidized products of sulfide by cyt.c-555 was identified as polysulfide. The reduced form of cyt.c-555 was suggested to be oxidized coupled with cyt.c oxidase which is tolerant to sulfide. 相似文献
7.
Hoh JF Withers KW Zhong WW 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2008,178(3):279-284
The effect of drug-induced hypothyroidism on ventricular myosin gene expression was explored in a small marsupial, Antechinus flavipes. Pyrophosphate gel electrophoresis, SDS-PAGE and western blotting were used to analyse changes in native myosin isoforms
and myosin heavy chains (MyHCs) in response to hypothyroidism. In some animals, five instead of the normal three native myosin
components were found: V1a, V1b,V1c, V2 and V3, in order of decreasing mobility. In western blots, V1a, V1b, and V1c reacted with anti-α-MyHC antibody, but not with anti-β-MyHC, whereas V2 and V3 reacted with anti-β-MyHC antibody. SDS-PAGE of the unusual ventricular myosins revealed three MyHC isoforms, two of which
bound anti-α-MyHC antibody while the third bound anti-β-MyHC antibody. We conclude that V1a, V1b, V1c are triplets arising from the dimerization of two distinct α-MyHC isoforms. Hypothyroidism, verified by metabolic studies,
decreased α-MyHC content significantly (t-test, P < 0.001) from 91.6 ± 5.9% (SEM, n = 4) in control animals to 67.2 ± 5.7% (SEM, n = 4) in hypothyroid animals, with a concomitant increase in β-MyHC content. We conclude that in adult marsupials, ventricular
myosins are also responsive to changes in the thyroid state as found in eutherians, and suggest that evolution of the molecular
mechanisms underlying this thyroid responsiveness predate the divergence of marsupials and eutherians. 相似文献
8.
C-phycocyanin and allophycocyanin from the red alga Rhodella violacea were investigated by electron microscopy and biochemical methods using samples taken from the same fractions.The molecular weights of the native biliprotein aggregates C-phycocyanin and allophycocyanin are about 139,000 (140,000) and 130,000 (145,000) as revealed by calibrated gel chromatography, gradient gel electrophoresis and morphological measurements on the basis of an average protein packing density. These molecular weights are direct evidence for a trimeric aggregation form ()3 of these biliproteins. Independently, their monomers were determined to be about 34,400 (C-phycocyanin) and 33,900 (allophycocyanin).C-phycocyanin and allophycocyanin are ringshaped, six-membered, biliprotein aggregates with dimensions of about 10.2×3.0 nm and 10.0×3.0 nm, respectively. The aggregates are made up of six subunits, 3 and 3, which are assumed to be associated in alternating positions. They are arranged in regular hexagons in C6 symmetry. Hexameric aggregates ()6, so far only isolated for C-phycocyanin, originate by face to face association of two trimeric aggregates. 相似文献
9.
ZENG ZonghaoJIN LeiLI HongminHU Zhong WANG Dacheng 《中国科学:生命科学英文版》1998,41(4):413-418
Crystals of pokeweed antiviral protein (PAP) from seeds of Phytolacca americana with high diffraction ability were grown from high protein concentration (100 mg/mL) solution at high temperature (33℃). The crystal structure was solved by use of molecular replacement method and refined by use of molecular dynamic method at 0 25 nm to an R factor of 18.15% with standard deviations from standard geometry of 0.001 6 nm and 2.04° for bond lengths and bond angles, respectively. Comparison with two other PAPs revealed, near the active center, a sequence and structure variable region, consisting of the loop connecting the fifth β strand with the second α helix and including a proposed active residue, suggesting this loop probably to be related to difference in activity.$$$$ 相似文献
10.
Aimed at achieving a good understanding of the 3-dimensional structures of human α1A-adrenoceptor (α1A-AR), we have successfully developed its homology model based on the crystal structure of β2-AR. Subsequent structural refinements were performed to mimic the receptor’s natural membrane environment by using molecular
mechanics (MM) and molecular dynamics (MD) simulations in the GBSW implicit membrane model. Through molecular docking and
further simulations, possible binding modes of subtype-selective α1A-AR antagonists, Silodosin, RWJ-69736 and (+)SNAP-7915, were examined. Results of the modeling and docking studies are qualitatively
consistent with available experimental data from mutagenesis studies. The homology model built should be very useful for designing
more potent subtype-selective α1A-AR antagonists and for guiding further mutagenesis studies.
Figure The superposition of β2-AR crystal structure (gold ribbons) and α1A-AR homology model (blue ribbons) 相似文献
11.
Milgrom YM 《Biochemistry. Biokhimii?a》2011,76(11):1253-1261
MgADP and MgATP binding to catalytic sites of βY341W-α3β3Γ subcomplex of F1-ATPase from thermophilic Bacillus PS3 has been assessed using their effect on the enzyme inhibition by 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl). It
was assumed that NBD-Cl can inhibit only when catalytic sites are empty, and inhibition is prevented if a catalytic site is
occupied with a nucleotide. In the absence of an activator, MgADP and MgATP protect βY341W-α3β3Γ sub-complex from inhibition by NBD-Cl by binding to two catalytic sites with an affinity of 37 μM and 12 mM, and 46 μM and
15 mM, respectively. In the presence of an activator lauryldimethylamine-N-oxide (LDAO), MgADP protects βY341W-α3β3Γ subcomplex from inhibition by NBD-Cl by binding to a catalytic site with a K
d of 12 mM. Nucleotide binding to a catalytic site with affinity in the millimolar range has not been previously revealed in
the fluorescence quenching experiments with βY341W-α3β3Γ subcomplex. In the presence of activators LDAO or selenite, MgATP protects βY341W-α3β3Γ subcomplex from inhibition by NBD-Cl only partially, and the enzyme remains sensitive to inhibition by NBD-Cl even at MgATP
concentrations that are saturating for ATPase activity. The results support a bi-site mechanism of catalysis by F1-ATPases. 相似文献
12.
13.
In recent years, it has become clear that the neuronal nicotinic acetylcholine receptor (nAChR) is a valid target in the treatment
of a variety of diseases, including Alzheimer’s disease, anxiety, and nicotine addiction. As with most membrane proteins,
information on the three-dimensional (3D) structure of nAChR is limited to data from electron microscopy, at a resolution
that makes the application of structure-based design approaches to develop specific ligands difficult. Based on a high-resolution
crystal structure of AChBP, homology models of the extracellular domain of the neuronal rat and human nAChR subtypes α4β2
and α7 (the subtypes most abundant in brain) were built, and their stability assessed with molecular dynamics (MD). All models
built showed conformational stability over time, confirming the quality of the starting 3D model. Lipophilicity and electrostatic
potential studies performed on the rat and human α4β2 and α7 nicotinic models were compared to AChBP, revealing the importance
of the hydrophobic aromatic pocket and the critical role of the α-subunit Trp—the homolog of AChBP-Trp 143—for ligand binding.
The models presented provide a valuable framework for the structure-based design of specific α4β2 nAChR subtype ligands aimed
at improving therapeutic and diagnostic applications.
Figure Electrostatic surface potential of the binding site cavity of the neuronal nicotinic acetylcholine receptor (nAChR). Nicotinic
models performed with the MOLCAD program: a rat α7, b rat α4β2, c human α7, d human α4β2. All residues labeled are part of the α7 (a,c) or α4 (b,d) subunit with the exception of Phe 117, which belongs to subunit β2 (d). Violet Very negative, blue negative, yellow neutral, red very positive 相似文献
14.
A new phycoerythrin, SCH-phycoerythrin, was purified from Synechococcus sp. ECS-18 by DEAE-Sephacel anion exchange chromatography and Sephacryl S-300 gel filtration. The protein pigment had an
absorbance maximum at 542 nm and a fluorescence maximum at 565 nm. The native molecular mass was approximately 219 kDa as
determined by gel filtration, and sodium dodecyl sulfate polyacrylamide gel electrophoresis demonstrated the presence of two
subunits, with molecular mass of 19 and 17.9 kDa. These observations are consistent with the (αβ)6 subunit composition that is characteristic of phycoerythrins. The α- and β-subunits showed immunological identity by Ouchterlony
double immunodiffusion with an anti-phycoerythrin antiserum. The DNA sequence of the SCH-phycoerythrin gene was determined
by PCR amplification using primers based on the conserved N-terminal amino acid sequence of the α- and β-subunits of phycoerythrins. 相似文献
15.
Summary A Monte Carlo simulation is proposed to study the dynamics of helper T-cells (N
H) and viral (N
V) populations in an immune response model relevant to HIV. Cellular states are binary variables and the interactions are described
by logical expressions. Viral population shows a nonmonotonic growth before reaching a constant value while helper T-cells
grow to a constant after a relaxation/reaction time. Initially, the population of helper cells grows with time with a power-law,
N
H ∼t
β, before reaching the steady-state; the growth exponent β increases systematically (β ≈ 1 – 2) with the mutation rate (P
mut≈0.1–0.4). The critical recovery time (t
c) increases exponentially with the viral mutation, t
c≈Ae
αP
mut
, with α=4.52±0.29 in low mutation regime and α=15.21±1.41 in high mutation regime. The equilibrium population of helper T-cell
declines slowly with P
mut and collapses at ∼ 0.40; the viral population exhibits a reverse trend, i.e., a slow increase before the burst around the
same mutation regime. 相似文献
16.
J. Seifert 《Folia microbiologica》1973,18(5):386-389
Proceeding from three previously derived expressions for the intensity of nitrification in soil as a function of time (logΣN=K.logt+q), as a function of incubation moisture (logΣN=A.pF
i+B), as a function of initial moisture (logΣN=C.pF
v+D), it was shown that the nitrification intensity as a function of time and of moisture can be expressed by the bilinear function
log ΣN=a.pF
i.logT+b.pF
i+c.logt+d; as a function of time and of initial moisture by the bilinear function logΣ=N=a.pF
v.logt+b.pF
v+c.logt+d; as a function of initial and incubation moisture by the bilinear function log ΣN=a.pF
ipF
v+b.pF
i+c.pF
v+d. The intensity of nitrification as a function of time, incubation moisture and initial moisture may be expressed by the multilinear
function log ΣN=a.pF
i.pF
v.logt+b.pF
i.pF
v+c.pF
i.logt+d.pF
v.logt+e .pF
i+f.pF
v=g.logt+h. This function is valid for all the incubation moistures lying between pF
i 3.0 and 4.0 and for all initial moistures between 3.5 and 5.9 provided that the incubation temperature remains constant. 相似文献
17.
The development of desiccation tolerance by vegetative tissues was an important step in the plants’ conquest of land. To counteract
the oxidative stress generated under these conditions the xanthophyll cycle plays a key role. Recent reports have shown that
desiccation itself induces de-epoxidation of xanthophyll cycle pigments, even in darkness. The aim of the present work was
to study whether this trait is a common response of all desiccation-tolerant plants. The xanthophyll cycle activity and the
maximal photochemical efficiency of PS II (F
v/F
m) as well as β-carotene and α-tocopherol contents were compared during slow and rapid desiccation and subsequent rehydration
in six species pairs (with one desiccation-sensitive and one desiccation-tolerant species each) belonging to different taxa.
Xanthophyll cycle pigments were de-epoxidised in darkness concomitantly with a decrease in F
v/F
m during slow dehydration in all the desiccation-tolerant species and in most of the desiccation-sensitive ones. De-epoxidation
was reverted in darkness by re-watering in parallel with the recovery of the initial F
v/F
m. The stability of the β-carotene pool confirmed that its hydroxylation did not contribute to zeaxanthin formation. The α-tocopherol
content of most of the species did not change during dehydration. Because it is a common mechanism present in all the desiccation-tolerant
taxa and in some desiccation-sensitive species, and considering its role in antioxidant processes and in excess energy dissipation,
the induction of the de-epoxidation of xanthophyll cycle pigments upon dehydration in the dark could be understood as a desiccation
tolerance-related response maintained from the ancestral clades in the initial steps of land occupation by plants. 相似文献
18.
T. M. Falk W. Villwock L. Renwrantz 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(1):9-16
Haemoglobins of five tilapiine species of the genera Oreochromis and Sarotherodon were investigated. By gel filtration chromatography a molecular weight of 67–69 kDa was determined for the tetrameric molecules
which remained stable between pH 5.0 and pH 9.1. When subjected to sodium dodecyl sulphate-Urea-polyacrylamide gel electrophoresis
(PAGE), haemoglobins of all species each were split into monomers of three different molecular weights ranging between 16.3
kDA and 17.6 kDa. Subsequently, isoelectric focusing separated haemolysates into about 23 differently charged tetrameric haemoglobins
that were arranged in species-specific patterns. This diversity was shown to result from the occurrence of different types
of globin chains. By acidic urea PAGE a total of seven major α-globins and five major β-globins were detected and species-characteristic
chain variants were identified. To determine the globin chain composition of particular haemoglobin tetramers, 26 bands were
isolated by isoelectric focusing and analysed by acidic urea PAGE. Tetramers consisted of doublets of identical α- and identical
β-chains (α2β2, symmetric tetramers), or combinations of three (α2ββ*; αα*β2) or four (αα*ββ*) distinct chains (asymmetric tetramers). Finally, globin chains of Oreochromis niloticus were subjected to partial N-terminal amino acid sequencing. Differences in the composition of the three major β-chains could
be shown, whereas the α-chains were N-terminally blocked.
Accepted: 12 September 1997 相似文献
19.
Uchida H Hojyo M Fujii Y Maeda Y Kajimura R Yamanaka H Sakurai A Sakakibara M Aisaka K 《Applied microbiology and biotechnology》2007,74(4):805-812
Formate oxidase was found in cell-free extracts of Debaryomyces vanrijiae MH201, a soil isolate. After purification by column chromatography, the preparation showed a protein band corresponding to
a molecular mass (MM) of 64 kDa on sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The MM, estimated by a gel filtration,
was 99 kDa. The preparation showed two and three bands on isoelectric focusing under denaturing and native conditions, respectively.
These results suggest that the preparation contained three isoforms, each of which might be composed of αα, αβ, and ββ subunits
with apparently similar MM. The preparation acted on formate with K
m and V
max values of 11.7 mM and 262 μmol min−1 mg−1, respectively, at pH 4.5 and 25°C, but showed no evidence of activity on the other compounds tested. The optimum pH and temperature
were pH 4.0 and 35°C, respectively. The preparation showed activities of 85% of the initial activity after storage at pH 6.0
and 4°C for 8 weeks. When 10 mM formaldehyde was reacted with 2.0 U ml−1 of the enzyme preparation at pH 5.5 and room temperature in the presence of 2.0 U ml−1 of a microbial aldehyde oxidase and 100 U ml−1 of catalase for 180 min, neither of formate nor formaldehyde was detected, suggesting that the reaction involved the quantitative
conversion of formaldehyde to carbon dioxide. 相似文献
20.
The endophytic cyanobacterium, Anabaena azollae, isolated from laboratory cultures of Azolla caroliniana Willd., contains three spectroscopically distinct biliproteins. About 70% of the biliprotein is c-phycocyanin (max 610 nm) and 13% is allophycocyanin (max 647 nm, shoulder 620 nm). A third pigment corresponds to phycoerythrocyanin (max 570 nm, shoulder 590 nm). In very dilute solutions of allophycocyanin, at constant pH and buffer strength, the 647 nm maximum disappears and a single max occurs at 615–620 nm. The 647 nm absorption maximum reappears upon concentrating the dilute solution. Very dilute solutions of phycoerythrocyanin exhibit a broad peak between 570 and 590 nm. Absorption spectra of c-phycocyanin are not significantly altered upon dilution. Fluorescence emission maxima of phycoerythrocyanin, c-phycocyanin, and allophycocyanin occur at 630 nm, 643 nm and 660 nm respectively, using 540 nm excitation. Two subunits, of molecular weight 16,500 () and 20,600 (), are seen in c-phycocyanin upon dissociation with SDS. Dissociation of allophycocyanin and phycoerythrocyanin with SDS yields one sizeclass of subunits, with a molecular weight of about 17,500 for allophycocyanin and 18,000 for phycoerythrocyanin.Contribution No. 684
Offprint requests to: G. A. Peters 相似文献