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1.
Tadeusz Pawelczyk Renata Kowara Filip Golebiowski Andrzej Matecki 《Protein expression and purification》2000,18(3):320
The fragile histidine triad (Fhit) protein is a homodimeric protein with diadenosine 5′,5-P1,P3-triphosphate (Ap3A) asymmetrical hydrolase activity. We have cloned the human cDNA Fhit in the pPROEX-1 vector and expressed with high yield in Escherichia coli with the sequence Met-Gly-His6-Asp-Tyr-Asp-Ile-Pro-Thr-Thr followed by a rTEV protease cleavage site, denoted as “H6TV,” fused to the N-terminus of Fhit. Expression of H6TV–Fhit in BL21(DE3) cells for 3 h at 37°C produced 30 mg of H6TV–Fhit from 1 L of cell culture (4 g of cells). The H6TV–Fhit protein was purified to homogeneity in a single step, with a yield of 80%, using nickel-nitrilotriacetate resin and imidazole buffer as eluting agent. Incubation of H6TV–Fhit with rTEV protease at 4°C for 24 h resulted in complete cleavage of the H6TV peptide. There were no unspecific cleavage products. The purified Fhit protein could be stored for 3 weeks at 4°C without loss of activity. The pure protein was stable at −20°C for at least 18 months when stored in buffer containing 25% glycerol. Purified Fhit was highly active, with a Km value for Ap3A of 0.9 μM and a kcat(monomer) value of 7.2 ± 1.6 s−1 (n = 5). The catalytic properties of unconjugated Fhit protein and the H6TV–Fhit fusion protein were essentially identical. This indicates that the 24-amino-acid peptide containing the six histidines fused to the N-terminus of Fhit does not interfere in forming the active homodimers or in the binding of Ap3A. 相似文献
2.
Christoph J. Albrecht Florian M. Stumpf Lena Krüger Marie L. Niedermeier Florian Stengel Andreas Marx 《Journal of peptide science》2023,29(3):e3458
Intracellular dinucleoside polyphosphates (NpnNs) have been known for decades but the functional role remains enigmatic. Diadenosine triphosphate (Ap3A) is one of the most prominent examples, and its intercellular concentration was shown to increase upon cellular stress. By employment of previously reported Ap3A-based photoaffinity-labeling probes (PALPs) in chemical proteomics, we investigated the Ap3A interactome in the human lung carcinoma cell line H1299. The cell line is deficient of the fragile histidine triade (Fhit) protein, a hydrolase of Ap3A and tumor suppressor. Overall, the number of identified potential interaction partners was significantly lower than in the previously investigated HEK293T cell line. Gene ontology term analysis revealed that the identified proteins participate in similar pathways as for HEK293T, but the percentage of proteins involved in RNA-related processes is higher for H1299. The obtained results highlight similarities and differences of the Ap3A interaction network in different cell lines and give further indications regarding the importance of the presence of Fhit. 相似文献
3.
Control of 5′,5′-Dinucleoside Triphosphate Catabolism by APH1, a Saccharomyces cerevisiae Analog of Human FHIT
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Josiane Chen Annie Brevet Sylvain Blanquet Pierre Plateau 《Journal of bacteriology》1998,180(9):2345-2349
The putative human tumor suppressor gene FHIT (fragile histidine triad) (M. Ohta et al., Cell 84:587–597, 1996) encodes a protein behaving in vitro as a dinucleoside 5′,5′′′-P1,P3-triphosphate (Ap3A) hydrolase. In this report, we show that the Saccharomyces cerevisiae APH1 gene product, which resembles human Fhit protein, also hydrolyzes dinucleoside 5′,5′-polyphosphates, with Ap3A being the preferred substrate. Accordingly, disruption of the APH1 gene produced viable S. cerevisiae cells containing reduced Ap3A-hydrolyzing activity and a 30-fold-elevated Ap3N concentration. 相似文献
4.
Contractile function of rat myocardium is less susceptible to hypoxia/reoxygenation after acute infarction 总被引:6,自引:0,他引:6
Bagchi M Balmoori J Ye X Bagchi D Ray SD Stohs SJ 《Molecular and cellular biochemistry》2001,226(1-2):49-55
The FHIT (fragile histidine triad) gene located at chromosome 3p14.2 has been proposed as a candidate tumor suppressor gene in human cancers. Fhit protein with the diadenosine 5',5'-P1,P3-triphosphate (Ap3A) hydrolase activity is the protein product of FHIT gene. The way in which Fhit exerts its tumor suppressor activity and the relationship of the Ap3A hydrolase activity to tumor suppression are not known. As a step toward understanding of the Fhit function in the cell we have explored its intracellular localization and distribution in the rat tissues. Data obtained from immunoblot analysis showed that Fhit protein was most abundant in spleen and brain. Moderate amount of Fhit was detected in kidney and liver, whereas the level of Fhit protein in heart, skeletal muscle and kidney glomeruli was undetectable. RT-PCR performed on RNA isolated from these tissues showed no product, whereas the level of Fhit mRNA in spleen, brain, kidney, liver and lung correlated with the Fhit protein level. The immunoblot analysis performed on subcellular fractions of various rat tissues obtained by differential and density-gradient centrifugation showed that Fhit protein was localized exclusively in nucleus and at the plasma membrane. Presented data showing nuclear and plasma membrane localization of Fhit may support the hypothesis concerning Fhit as a signaling molecule. 相似文献
5.
Rv2613c is a diadenosine 5′,5?-P1,P4-tetraphosphate (Ap4A) phosphorylase from Mycobacterium tuberculosis H37Rv. Sequence analysis suggests that Rv2613c belongs to the histidine triad (HIT) motif superfamily, which includes HIT family diadenosine polyphosphate (ApnA) hydrolases and Ap4A phosphorylases. However, the amino acid sequence of Rv2613c is more similar to that of HIT family ApnA hydrolases than to that of typical Ap4A phosphorylases. Here, we report the crystal structure of Rv2613c, which is the first structure of a protein with ApnA phosphorylase activity, and characterized the structural basis of its catalytic activity. Our results showed that the structure of Rv2613c is similar to those of other HIT superfamily proteins. However, Asn139, Gly146, and Ser147 in the active site of Rv2613c replace the corresponding Gln, Gln, and Thr residues that are normally found in HIT family ApnA hydrolases. Furthermore, analyses of Rv2613c mutants revealed that Asn139, Gly146, and Ser147 are important active-site residues and that Asn139 has a critical role in catalysis. The position of Gly146 might influence the phosphorylase activity. In addition, the tetrameric structure of Rv2613c and the presence of Trp160 might be essential for the formation of the Ap4A binding site. These structural insights into Rv2613c may facilitate the development of novel structure-based inhibitors for treating tuberculosis. 相似文献
6.
Riadh Ben Salah Ali Gargouri Robert Verger Youssef Gargouri Hafedh Mejdoub 《World journal of microbiology & biotechnology》2009,25(8):1375-1384
The sequence corresponding to the mature lipase of Rhizopus oryzae WPG (ROLw) was subcloned in the pPIC9K expression vector, with a strong AOX1 promoter, to construct a recombinant lipase protein containing six histidine residues at the N-terminal. The His-tagged lipase
was expressed in Pichia Pastoris X33 and purified to homogeneity by a simple, one-step purification protocol using immobilized metal affinity chromatography (Ni-NTA
resin). High level expression of the lipase by Pichia Pastoris X33 cells harbouring the lipase gene containing expression vector was observed upon induction with 2.5 g/l methanol at 28°C;
the specific activity of the purified His6-ROLw was 1,500 or 760 U/mg using olive oil emulsion or tributyrin as substrates, respectively. To check the importance of
Asn 134 His substitution in the affinity and substrate selectivity of ROLw, the mutant His6-ROLw-N134H was overexpressed in Pichia Pastoris X33 and purified with the same nickel metal affinity column. The specific activity of the purified His-tagged ROLw-N134H
was 5,900 and 35 U/mg using olive oil emulsion or tributyrin as substrate. A comparative study of the wild type (His6-ROLw) and the mutant (His6-ROLw-N134H) proteins was carried out. A 3D structure model of ROLw was built using the RNL structure as template. We have
concluded that a slight increase in the exposed hydrophilic residues on the surface of ROLw as compared to RNL (ROLwN134H)
could be responsible for a higher selectivity of ROlw for long and short chain triacylglycerols at the lipid/water interface
and then explaining the importance of Asn 134 for the chain length specificity of ROLw. This property is quite rare among
Rhizopus lipases and gives this new lipase great potential for use in the field of biocatalysis. 相似文献
7.
Feng R Zhai WL Yang HY Jin H Zhang QX 《Biochemical and biophysical research communications》2011,411(2):299-304
Porphyromonas gingivalis acquires heme through an outer-membrane heme transporter HmuR and heme-binding hemophore-like lipoprotein HmuY. Here, we compare binding of iron(III) mesoporphyrin IX (mesoheme) and iron(III) deuteroporphyrin IX (deuteroheme) to HmuY with that of iron(III) protoporphyrin IX (protoheme) and protoporphyrin IX (PPIX) using spectroscopic methods. In contrast to PPIX, mesoheme and deuteroheme enter the HmuY heme cavity and are coordinated by His134 and His166 residues in a fully analogous way to protoheme binding. However, in the case of deuteroheme two forms of HmuY–iron porphyrin complex were observed differing by a 180° rotation of porphyrin about the α-γ-meso-carbon axis. Since the use of porphyrins either as active photosensitizers or in combination with antibiotics may have therapeutic value for controlling bacterial growth in vivo, it is important to compare the binding of heme derivatives to HmuY. 相似文献
8.
C. Gamini Kannangara Ute C. Vothknecht Mats Hansson Diter von Wettstein 《Molecular & general genetics : MGG》1997,254(1):85-92
Magnesium chelatase catalyses the insertion of Mg2+ into protoporphyrin and is found exclusively in organisms which synthesise chlorophyll or bacteriochlorophyll. Soluble protein
preparations containing >10 mg protein/ml, obtained by gentle lysis of barley plastids and Rhodobacter sphaeroplasts, inserted Mg2+ into deuteroporphyrin IX in the presence of ATP at rates of 40 and 8 pmoles/mg protein per min, respectively. With barley
extracts optimal activity was observed with 40 mM Mg2+. The activity was inhibited by micromolar concentrations of chloramphenicol. Mutations in each of three genetic loci, Xantha-f, -g and -h, in barley destroyed the activity. However, Mg-chelatase activity was reconstituted in vitro by combining pairwise the plastid
stroma protein preparations from non-leaky xantha-f, -g and -h mutants. This establishes that, as in Rhodobacter, three proteins are required for the insertion of magnesium into protoporphyrin IX in barley. These three proteins, Xantha-F,
-G and -H, are referred to as Mg-chelatase subunits and they appear to exist separate from each other in vivo. Active preparations
from barley and Rhodobacter yielded pellet and supernatant fractions upon centrifugation for 90 min at 272 000 × g. The pellet and the supernatant were inactive when assayed separately, but when they were combined activity was restored.
Differential distribution of the Mg-chelatase subunits in the fractions was established by in vitro complementation assays
using stroma protein from the xantha-f, -g, and -h mutants. Xantha-G protein was confined to the pellet fraction, while Xantha-H was confined to the supernatant. Reconstitution
assays using purified recombinant BchH, BchI and partially purified BchD revealed that the pellet fraction from Rhodobacter contained the BchD subunit. The pellet fractions from both barley and Rhodobacter contained ribosomes and had an A260:A280 ratio of 1.8. On sucrose density gradients both Xantha-G and BchD subunits migrated with the plastid and bacterial ribosomal
RNA, respectively.
Received: 9 September 1996 / Accepted: 22 October 1996 相似文献
9.
Palmieri G Casbarra A Fiume I Catara G Capasso A Marino G Onesti S Rossi M 《Extremophiles : life under extreme conditions》2006,10(5):393-402
The archaeon Aeropyrum pernix grows optimally at 90°C and derives energy primarily from aerobic degradation of complex proteinaceous substrates. The ability of these nutrients to sustain growth is generally associated with the presence of oligopeptide transport systems, such as the well-known protein-dependent ATP-binding cassette (ABC) transporters. This study is concerned with the isolation and characterisation of the first archaeal oligopeptide-binding protein (OppAAp) from the extracellular medium of A. pernix. The protein shows a pI of 3.9 and a molecular mass of about 90 kDa under native conditions. By using a proteomic approach, the OppAAp-encoding gene was identified (APE1583) and about 55% of the protein amino-acid sequence was validated. The extracellular purified protein was able to efficiently bind oligopeptide substrates such as Xenopsin. The amount of a liganded peptide to OppAAp was about 70% at 90°C using a 1/100 (w/w) OppAAp/substrate ratio. Sequence comparisons showed a weak but significant similarity of OppAAp with bacterial oligopeptide binding proteins. Furthermore, APE1583 neighbouring genes encode for the cognate components of an ABC transport system, suggesting that these ORFs are organised in an operon-like structure, with OppAAp as the extracellular component for the uptake of oligopeptides. 相似文献
10.
Subplastidic preparations from cotyledons of cucumber (Cucumis sativus L.) were tested for their ability to synthesize protoporphyrin IX from the substrate 5-aminolevulinic acid. Envelope or thylakoid
membranes failed to synthesize protoporphyrin IX from the substrate 5-aminolevulinic acid. Stromal preparations synthesized
a very low amount of protoporphyrin IX. In a reconstitution experiment using stroma + envelope membranes, protoporphyrin IX
synthesis from 5-aminolevulinic acid was enhanced by 660% over that of stroma alone. However, when thylakoids were added to
the stroma + envelope mixture, protoporphyrin IX synthesis from 5-aminolevulinic acid was completely inhibited. In the reconstituted
stroma + envelope membrane mixture, the reducing agent dithiothreitol enhanced the protoporphyrin IX-synthesizing ability
and completely abolished the inhibition of protoporphyrin IX synthesis by thylakoids. This suggested that the oxidizing agents
usually associated with the thylakoid membranes inhibited protoporphyrin IX biosynthesis and the inhibition was alleviated
by the reducing power of dithiothreitol. This study exposes the weakness of in vitro reconstitution experiments in mimicking
the in vivo-conditions. Addition of ATP stimulated protoporphyrin IX synthesis by 50% in the supernatant fraction of chloroplast
lysate. This ATP-induced stimulation of protoporphyrin IX synthesis was due to the enhancement of the activities of uroporphyrinogen
decarboxylase and protoporphyrinogen oxidase, involved in tetrapyrrole biosynthesis. The ATP-induced stimulation of porphyrinogen
oxidase activity was an energy-dependent reaction.
Received: 21 March 2000 / Accepted: 9 May 2000 相似文献
11.
In order to examine the mediatory role of proton motive force (∆p) or proton ATPase in H2 production by Rhodobacter sphaeroides, ∆p was determined under anaerobic conditions in the dark, and the ATPase activity has been studied in R. sphaeroides strain A-10, isolated from Arzni mineral springs in Armenia. Membrane potential (∆φ) was measured from the distribution of
tetraphenylphosphonium cation; pH gradient (∆pH) was the difference between the external and cytoplasmic pH values, and the
latter was measured by 9-aminoacridine (9-AA) fluorescence changes. At pH 7.5, ∆φ was of −94 mV and the reversed ∆pH was +30 mV,
resulting in ∆p of −64 mV. The addition of N,N′-dicyclohexylcarbodiimide (DCCD), the F0F1–ATPase inhibitor, was not affect ∆φ. It was shown that ∆φ varies nearly linearly with ΔpH, ∆φ increased from −57.1 mV at
pH 6.0 to −103.8 mV at pH 8.0; it was compensated at high external pH by a reversed ∆pH, resulting in a low ∆p under anaerobic-dark
conditions. Intracellular ATP concentrations and energetic charge (EC) were measured to evaluate a metabolism activity of
R. sphaeroides. 相似文献
12.
Lu Sun Xin Wen Ying Tan Heyang Li Xing Yang Yuefang Zhao Baifan Wang Qiongyao Cao Congwei Niu Zhen Xi 《Amino acids》2009,37(3):523-530
Protoporphyrinogen IX oxidase (PPO), the last common enzyme of heme and chlorophyll biosynthesis, catalyses the oxidation
of protoporphyrinogen IX to protoporphyrin IX, with FAD as cofactor. Among PPO, Bacillus subtilis PPO (bsPPO) is unique because of its broad substrate specificity and resistance to inhibition by diphenylethers. Identification of
the activity of bsPPO would help us to understand the catalysis and resistance mechanisms. Based on the modeling and docking studies, we found
that Y366 site in bsPPO was adjacent to substrate and FAD. In order to evaluate the functional role of this site, three mutants Y366A Y366E and
Y366H were cloned and kinetically characterized. The efficiency of catalysis for Y366A and Y366H reduced to 10% of the wild-type
enzyme’s activity, while Y366E just retained 1%. Y366E shows large resistance (K
i = 153.94 μM) to acifluorfen. Molecular docking was carried out to understand the structure and functional relationship of
PPO. The experimental results from the site-directed mutagenesis are consistent with the computational studies. The residue
at position 366 is seemed to be responsible for substrate binding and catalysis and involved in herbicide resistance of bsPPO. 相似文献
13.
Aline Gomez Maqueo Chew Niels-Ulrik Frigaard Donald A. Bryant 《Photosynthesis research》2009,101(1):21-34
The first committed step in the biosynthesis of (bacterio-)chlorophyll is the insertion of Mg2+ into protoporphyrin IX by Mg-chelatase. In all known (B)Chl-synthesizing organisms, Mg-chelatase is encoded by three genes
that are homologous to bchH, bchD, and bchI of Rhodobacter spp. The genomes of all sequenced strains of green sulfur bacteria (Chlorobi) encode multiple bchH paralogs, and in the genome of Chlorobaculum tepidum, there are three bchH paralogs, denoted CT1295 (bchT), CT1955 (bchS), and CT1957 (bchH). Cba. tepidum mutants lacking one or two of these paralogs were constructed and characterized. All of the mutants lacking only one of these
BchH homologs, as well as bchS bchT and bchH bchT double mutants, which can only produce BchH or BchS, respectively, were viable. However, attempts to construct a bchH
bchS double mutant, in which only BchT was functional, were consistently unsuccessful. This result suggested that BchT alone is
unable to support the minimal (B)Chl synthesis requirements of cells required for viability. The pigment compositions of the
various mutant strains varied significantly. The BChl c content of the bchS mutant was only ~10% of that of the wild type, and this mutant excreted large amounts of protoporphyrin IX into the growth
medium. The observed differences in BChl c production of the mutant strains were consistent with the hypothesis that the three BchH homologs function in end product
regulation and/or substrate channeling of intermediates in the BChl c biosynthetic pathway.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
14.
Most biological substrates have distinctive sizes, shapes, and charge distributions which can be recognized specifically
by proteins. In contrast, myoglobin must discriminate between the diatomic gases O2, CO, and NO which are apolar and virtually the same size. Selectivity occurs at the level of the covalent Fe-ligand complexes,
which exhibit markedly different bond strengths and electrostatic properties. By pulling a water molecule into the distal
pocket, His64(E7)1 inhibits the binding of all three ligands by a factor of ∼10 compared to that observed for protoheme-imidazole complexes
in organic solvents. In the case of O2 binding, this unfavorable effect is overcome by the formation of a strong hydrogen bond between His64(E7) and the highly
polar FeO2 complex. This favorable electrostatic interaction stabilizes the bound O2 by a factor of ∼1000, and the net result is a 100-fold increase in overall affinity compared to model hemes or mutants with
an apolar residue at position 64. Electrostatic interaction between FeCO and His64 is very weak, resulting in only a two-
to three-fold stabilization of the bound state. In this case, the inhibitory effect of distal pocket water dominates, and
a net fivefold reduction in K
CO is observed for the wild-type protein compared to mutants with an apolar residue at position 64. Bound NO is stabilized ∼tenfold
by hydrogen bonding to His64. This favorable interaction with FeNO exactly compensates for the tenfold inhibition due to the
presence of distal pocket water, and the net result is little change in K
NO when the distal histidine is replaced with apolar residues. Thus, it is the polarity of His64 which allows discrimination
between the diatomic gases. Direct steric hindrance by this residue plays a minor role as judged by: (1) the independence
of K
O2, K
CO, and K
NO on the size of apolar residues inserted at position 64, and (2) the observation of small decreases, not increases, in CO
affinity when the mobility of the His64 side chain is increased. Val68(E11) does appear to hinder selectively the binding
of CO. However, the extent is no more than a factor of 2–5, and much smaller than electrostatic stabilization of bound O2 by the distal histidine.
Received, accepted: 23 May 1997 相似文献
15.
Structure determination of the adduct formed between the signal nucleotide diadenosine 5',5'-P1,P4-tetraphosphate (Ap4A) and cis-[Pt(NH3)2Cl2 总被引:1,自引:0,他引:1
Diadenosine 5′,5?-P1,P4-tetraphosphate (Ap4A), an intracellular regulatory nucleotide, has been found to react with the antitumor drug cis-diamminedichloroplatinum(II) and its aqua derivative to form a single complex. This complex has been purified by high-performance liquid chromatography and characterized by 1H-nmr and CD spectroscopy. In this complex, Ap4A takes a very particular conformation. It is an N7-N7 chelate of the metal with the two adenines in a head-to-head arrangement and an anti–anti conformation of the adenosines. Platinum chelation leads to a large decrease of the Ap4A conformational flexibility. 相似文献
16.
Role of the calcium-binding residues Asp231, Asp233, and Asp438 of Bacillus amyloliquefaciens α-amylase (BAA) on the enzyme properties was investigated by site-directed mutagenesis. The calcium-binding residues Asp231,
Asp233, and Asp438 were replaced with Asn, Asn, and Gly to produce the mutants D231N, D233N, and D438G, respectively. The
mutant amylases were purified to homogeneity and the purified enzymes was estimated to be approximately 58 kDa. The specific
activity for the mutant enzyme D233N was decreased by 84.8%, while D231N and D438G showed a decrease of 6.3% and 3.5% to that
of the wild-type enzyme, respectively. No significant changes in the K
m value, thermo-stability, optimum temperature, and optimum pH were observed in the mutations of D231N and D438G, while substitution
of Asp233 with Asn resulted in a dramatic reduction in the value of catalytic efficiency (K
cat/K
m) and thermo-stability at 60°C. The ranges of optimum temperature and optimum pH for D233N were also reduced to about 10°C
and 3–4 units, respectively. 相似文献
17.
Photon- and carbon-use efficiency in<Emphasis Type="Italic"> Ulva rigida</Emphasis> at different CO<Subscript>2</Subscript> and N levels 总被引:2,自引:0,他引:2
The seaweed Ulva rigida C. Agardh (Chlorophyta) was cultured under two CO2 conditions supplied through the air bubbling system: non-manipulated air and 1% CO2-enriched aeration. These were also combined with N sufficiency and N limitation, using nitrate as the only N source. High CO2 in U. rigida led to higher growth rates without increasing the C fixed through photosynthesis under N sufficiency. Quantum yields for charge separation at photosystem II (PSII) reaction centres (PSII) and for oxygen evolution (O2) decreased at high CO2 even in N-sufficient thalli. Cyclic electron flow around PSII as part of a photoprotection strategy accompanied by decreased antennae size was suspected. The new re-arrangement of the photosynthetic energy at high CO2 included reduced investment in processes other than C fixation, as well as in carbon diverted to respiration. As a result, quantum yield for new biomass-C production (growth) increased. The calculation of the individual quantum yields for the different processes involved allowed the completion of the energy flow scheme through the cell from incident light to biomass production for each of the CO2 and N-supply conditions studied.Abbreviations A total thallus absorptance - Apig absorptance due to pigments - Astr Absorptance due to non-pigmented structures - a* spectrally averaged in vivo absorption cross-section of chlorophyll a - CCM carbon-concentrating mechanism - Chl chlorophyll - DOC dissolved organic carbon - ETR electron transport rate - Fv/Fm optimum quantum yield for PSII charge separation - GP gross O2 evolution rate - kpig specific light absorption coefficient for pigments - kstr specific light absorption coefficient for non-pigmented structures - OP optimum O2 evolution rate - PFR photon fluence rate - POC particulate organic carbon - PS photosystem - qN non-photochemical quenching - qP photochemical quenching - growth quantum yield for new biomass-C production - O2 quantum yield for gross O2 evolution - PSII quantum yield for PSII charge separation 相似文献
18.
Studies of chloroplast development in four maize mutants defective in chlorophyll biosynthesis 总被引:3,自引:0,他引:3
Four mutants of maize (Zea mays L.) defective in chlorophyll biosynthesis have been analyzed with regard to the sites of their lesions and their effects on chloroplast development. Two yellow mutants, which accumulate no detectable porphyrin precursors when grown in darkness, are defective in the conversion of protoporphyrin IX to magnesium protoporphyrin. Etioplasts of these mutants may develop elaborate lamellar membrane systems, but prolamellar bodies are never observed. Two mutants, which are necrotic when grown under illumination, develop normal (non-necrotic) leaf tissue in the dark and accumulate a small amount of magnesium protoporphyrin monomethyl ester, corresponding approximately to the amount of protochlorophyllide accumulated by normal plants. The etioplasts of these mutants contain noncrystalline bodies. The implications of these observations with respect to chloroplast development are discussed.Journal Paper No. J-9136 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa Project No. 2035 相似文献
19.
Lyapina E. A. Machneva T. V. Larkina E. A. Tkachevskaya E. P. Osipov A. N. Mironov A. F. 《Biophysics》2010,55(2):296-300
The effect of photosensitizer with subsequent He-Ne (632.8 nm; 3 mW/cm2) laser irradiation on experimental skin wound healing has been studied. Pheophorbide a and protoporphyrin IX were used as photosensitizers. It was found that application of the photosensitizer and subsequent
laser irradiation, first, decreased the amount and the functional activity of leukocytes in the wound exudate and, second,
inhibited the SOD activity as compared with that of the control group. Moreover, pheophorbide and protoporphyrin practically
did not affect the total healing period but decreased the length of the inflammation stage. It was supposed that these effects
are related to generation of reactive oxygen species during irradiation. 相似文献
20.
Krutika Desai Subramanian Sivakami 《World journal of microbiology & biotechnology》2007,23(12):1661-1666
A superoxide dismutase (SOD) was purified from Spirulina platensis sonicate. The SOD was purified to homogeneity (48-fold and 0.24% yield) through ammonium sulphate precipitation and DEAE-52
anion exchange chromatography. The SOD from S. platensis appeared to be a homodimer with a molecular weight of 30 kDa and a subunit MW of 15 kDa as determined by both native polyacrylamide
gel electrophoresis and mass spectrometry. The enzyme activity was stable at pH 6.5–10.0 and 50 °C. Using group-specific chemical
modifying reagents, the amino acids arginine, histidine, tryptophan, tyrosine and aspartic acid were identified to be essential
for S. platensis SOD activity. The amino acid composition was found to lack methionine and cysteine. The inhibition of activity by H2O2 suggests that the enzyme may be an iron containing SOD. 相似文献