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W Fu

Publications and source records attributed to W Fu.

125 records · Page 7Linked to original sources
PubMed1993

The role and properties of the iron-sulfur cluster in Escherichia coli dihydroxy-acid dehydratase.

Dihydroxy-acid dehydratase has been purified from Escherichia coli and characterized as a homodimer with a subunit molecular weight of 66,000. The combination of UV visible absorption, EPR, magnetic circular dichroism, and resonance Raman spectroscopies indicates that the native enzyme contains a [4Fe-4S]2+,+ cluster, in contrast to spinach dihydroxy-acid dehydratase which contains a [2Fe-2S]2+,+ cluster (Flint, D. H., and Emptage, M. H. (1988) J. Biol. Chem. 263, 3558-3564). In frozen solution, the reduced [4Fe-4S]+ cluster has a S = 3/2 ground state with minor contributions from forms with S = 1/2 and possibly S = 5/2 ground states. Resonance Raman studies of the [4Fe-4S]2+ cluster in E. coli dihydroxy-acid dehydratase indicate non-cysteinyl coordination of a specific iron, which suggests that it is likely to be directly involved in catalysis as is the case with aconitase (Emptage, M. H., Kent, T. A., Kennedy, M. C., Beinert, H., and Münck, E. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 4674-4678). Dihydroxy-acid dehydratase from E. coli is inactivated by O2 in vitro and in vivo as a result of oxidative degradation of the [4Fe-4S]cluster. Compared to aconitase, the oxidized cluster of E. coli dihydroxy-acid dehydratase appears to be less stable as either a cubic or linear [3Fe-4S] cluster or a [2Fe-2S] cluster. Oxidative degradation appears to lead to a complete breakdown of the Fe-S cluster, and the resulting protein cannot be reactivated with Fe2+ and thiol reducing agents.

Amino Acid Sequence↗
PubMed1993

Resonance Raman studies of iron-only hydrogenases.

The nature of the iron-sulfur clusters in oxidized and reduced forms of Fe-only hydrogenases from Desulfovibrio vulgaris, Thermotoga maritima, and Clostridium pasteurianum has been investigated by resonance Raman spectroscopy. The results indicate the presence of ferredoxin-like [4Fe-4S]2+,+ and [2Fe-2S]2+,+ clusters in both T. maritima hydrogenase and C. pasteurianum hydrogenase I, but only [4Fe-4S]2+,+ clusters in D. vulgaris hydrogenase. This necessitates a reevaluation of the iron-sulfur cluster composition of C. pasteurianum hydrogenase I and indicates that the resonance Raman bands in the oxidized hydrogenase that were previously attributed to the hydrogen activating center [Macor, K. A., Czernuszewicz, R. S., Adams, M. W. W., & Spiro, T. G. (1987) J. Biol. Chem. 262, 9945-9947] arise from an indigenous [2Fe-2S]2+ cluster. No resonance Raman bands that could be uniquely attributed to the oxidized or reduced hydrogen activating center were observed. This suggests that the hydrogen activating center is a novel Fe center that is unrelated to any known type of Fe-S cluster.

Clostridium↗
PubMed1993

Maturation of dimeric viral RNA of Moloney murine leukemia virus.

We have analyzed the dimeric RNA present in Moloney murine leukemia virus (MoMuLV) particles. We found that the RNA in newly released virions is in a conformation different from that in mature virions, since it has a different electrophoretic mobility in nondenaturing agarose gels and dissociates into monomers at a lower temperature. On the basis of these results, we suggest that the RNA initially packaged into nascent virions is already dimeric but that the dimer undergoes a maturation process after the virus is released from the cell. In further experiments, we tested the possibility that this maturation event is linked to the maturation cleavage of the virion proteins, which is catalyzed by the viral protease (PR). We found that the dimeric RNA isolated from PR- mutant virions resembles that from immature virions: it has a lower electrophoretic mobility and a lower sedimentation rate, and it also dissociates at a lower temperature than does RNA from mature wild-type virions. When Kirsten sarcoma virus is rescued by a PR- mutant or by a somewhat leaky cysteine array mutant of MoMuLV, its RNA also exhibits a electrophoretic mobility lower than that in the wild-type pseudotype. These results suggest that the maturation of dimeric RNA in released virus particles requires the cleavage of the Gag precursor and the presence of an intact cysteine array in the released nucleocapsid protein.

3T3 Cells↗
PubMed1992

The role of the iron-sulfur cluster in Escherichia coli endonuclease III. A resonance Raman study.

Resonance Raman spectroscopy has been used to investigate the function and properties of the iron-sulfur cluster in Escherichia coli endonuclease III. Resonance Raman spectra in the Fe-S stretching region are indicative of a [4Fe-4S]2+ cluster with complete cysteinyl sulfur coordination, and vibrational assignments are made by analogy with bacterial ferredoxins. Minor changes in the vibrational frequencies of the modes primarily involving Fe-S(Cys) stretching accompany the binding of the inhibitor thymine glycol or an oligonucleotide containing a reduced apyrimidinic site. These changes are consistent with perturbation of the orientation of the ligating cysteinyl residues and rule out the possibility that the [4Fe-4S] cluster is directly involved with substrate or inhibitor binding. It is concluded that a structural role is most likely for the [4Fe-4S] cluster in endonuclease III.

Base Sequence↗
PubMed1992

Resonance Raman and magnetic circular dichroism studies of reduced [2Fe-2S] proteins.

The structural and electronic properties of the [2Fe-2S] clusters in reduced putidaredoxin, Spinacea oleracea ferredoxin, and Clostridium pasteurianum [2Fe-2S] ferredoxin have been investigated by resonance Raman and variable temperature magnetic circular dichroism spectroscopies. Both techniques are shown to provide diagnostic fingerprints for identifying [2Fe-2S]+ clusters in more complex multicomponent metalloenzymes. The Fe-S stretching modes of oxidized and reduced putidaredoxin are assigned via 34S and D2O isotope shifts and previous normal mode calculations for adrenodoxin (Han, S., Czernuszewicz, R. S., Kimura, T., Adams, M. W. W., and Spiro, T. G. (1989) J. Am. Chem. Soc. 111, 3505-3511). The close similarity in the resonance Raman spectra of reduced [2Fe-2S] centers, in terms of both the vibrational frequencies and enhancement profiles of the Fe-S stretching modes, permits these assignments to be generalized to all clusters of this type. Modes primarily involving Fe(III)-S(Cys) stretching are identified in all three reduced [2Fe-2S] proteins, and the frequencies are rationalized in terms of the conformation of the cysteine residues ligating the Fe(III) site of the localized valence reduced cluster. D2O isotope shifts indicate few, if any, amide NH-S hydrogen bond interactions involving the cysteines ligating the Fe(III) site. Preliminary resonance Raman excitation profiles suggest assignments for the complex pattern of electronic bands that comprise the low temperature magnetic circular dichroism spectra of the reduced proteins. S----Fe(III) and Fe(II)----S charge transfer, Fe d-d, and Fe(II)----Fe(III) intervalence bands are identified.

Adrenodoxin↗
PubMed1992

[Surveillance of infectious diseases among the persons going abroad through Harbin Port].

This paper reported the results of the health examination of 7447 persons going abroad and 70 persons returning home. The results showed that 349 cases carried HBsAg (with the positive rate 4.7%), and 41 cases with pulmonary tuberculosis (with the positive rate 0.6%), 4 cases with venereal disease (with the positive rate 0.05%). No AIDS and syphilis cases were detected. Suitable measures were taken for the these cases to meet the goal of surveillance.

Carrier State↗
PubMed1992

[Effects of mixture of Astragalus membranaceus, Fructus Ligustri lucidi and Eclipta prostrata on immune function in mice].

A Chinese medicine mixture containing Astragalus membranaceus, Fructus Ligustri Lucidi and Eclipta prostrata(AFE), was fed to mice 9g/kg, 20g/kg, respectively for seven days. Observe the effects of AFE on the immune function in mice. The experiment showed that the two dosages of AFE could obviously raise the conversion percentage of lymphocytes (P < 0.01) and serum IgG level (41%-47%) of the mice. The weights of the thymus and spleensed increased in the two groups compared with those in the normal control. The larger dosage of AFE could also raise activity of Adenosine Deaminase (ADA) obviously (P < 0.01). AFE turned out a resistance to the immunosuppressive effect caused by cyclophosphamide.

Adenosine Deaminase↗
PubMed1992

[Effect of electroacupuncture on myocardial oxygen metabolism and pH of coronary sinus blood during experimental angina pectoris].

The experiments were performed on 30 healthy mongrel dogs, intubation was taken in the left anterior descending coronary (LAD), the blood in carotid was transported to LAD through a peristalic pump, the blood flow was reduced to 3-5 ml/min, thus acute myocardial ischemia was produced. Basing on this condition, 0.1-0.16 ml bradykinin (2 ug/ml) was given into LAD coronary before recording to produce angina pectoris. The effects of electroacupuncture (EA) at "Neiguan" area on myocardial oxygen metabolism, pH of coronary sinus blood and myocardial contractile force were observed (EA intensity 5 volts, frequency 1-20 Hz). The results are as follows: 1. EA could reduce obviously A-V difference of blood oxygen capacity (Ca-vO2) and the rate of myocardium extracting oxygen (O2E), thus reduced obviously oxygen consumption of ischemic myocardium. 2. EA could reduce V-A difference of carbon dioxide partial pressure (Pv-aCO2), prevent the decrease of pH of coronary sinus blood (PHv), this indicated that EA could prevent accumulation of acidic metabolic products. 3. EA could increase myocardial developed tension (DT) of ischemic area, strengthen myocardial contractile force of ischemic area. Above results indicated that EA could reduce oxygen consumption of ischemic myocardium, prevent the decrease of pH of coronary sinus blood, thus myocardial cell acidosis was prevented, myocardial contractile force was strengthened. It might be the mechanism of acupuncture treating coronary heart disease.

Angina Pectoris↗
PubMed1991

Assembly of the iron-sulfur protein into the cytochrome b-c1, complex of yeast mitochondria.

The assembly of the iron-sulfur protein into the cytochrome bc1 complex after import and processing of the precursor form into mitochondria in vitro was investigated by immunoprecipitation of the radiolabeled iron-sulfur protein from detergent-solubilized mitochondria with specific antisera. After import in vitro, the labeled mature form of the iron-sulfur protein was immunoprecipitated by antisera against both the iron-sulfur protein and the entire bc1 complex from mitochondria solubilized with either Triton X-100 or dodecyl maltoside. After sodium dodecyl sulfate solubilization of mitochondria, however, the antiserum against the iron-sulfur protein, but not that against the bc1 complex, immunoprecipitated the radiolabeled iron-sulfur protein. These results suggest that in mitochondria the mature form of the iron-sulfur protein is assembled with other subunits of the bc1 complex that are recognized by the antiserum against the bc1 complex. By contrast, the intermediate and precursor forms of the iron-sulfur protein that accumulated in the matrix when proteolytic processing was blocked with EDTA and o-phenanthroline were not efficiently assembled into the bc1 complex. The import and processing of the iron-sulfur protein also occurred in mitochondria lacking either cytochrome b (W-267) or the iron-sulfur protein (JPJ1). The mature form of the iron-sulfur protein was immunoprecipitated by antisera against the bc1 complex or core protein I after import in vitro into these mitochondria, suggesting that the mature form is associated with other subunits of the bc1 complex in these strains.

Biological Transport↗
PubMed1991

Spectroscopic evidence for a [3Fe-4S] cluster in spinach glutamate synthase.

The combination of low temperature EPR, magnetic circular dichroism, and resonance Raman spectroscopies reveals the presence of a single [3Fe-4S]+,0 center as the sole iron-sulfur prosthetic group in glutamate synthase from spinach leaves. The electronic, magnetic, and structural properties of the oxidized and reduced cluster are analogous with those of similar clusters in bacterial ferredoxins. It was not possible to convert the [3Fe-4S] cluster to a [4Fe-4S] cluster by incubating with iron under reducing conditions. Taken together with the published amino acid sequence data for plant and bacterial glutamate synthases, this suggests that the [3Fe-4S] cluster is not an isolation artifact resulting from oxidative degradation of a [4Fe-4S] cluster. The likelihood that a [3Fe-4S] cluster is an intrinsic component of all plant and bacterial glutamate synthases is discussed.

Circular Dichroism↗
PubMed1991

[Monitoring and controlling of renal transplant infection].

Infection is still the leading cause of death in renal transplantation. How to control it is an urgent problem to be solved. Bacteria culture, computerized monitoring methods, OKT monoclonal antibody techniques and radioimmunoassay (RIA) were applied to study the cause, monitoring and prevention of the infection. The result showed: Helper/suppressor lymphocyte ratio equalling 1.08 could be taken as a threshold value for infection diagnosis. 22 patients were colonized by Gram-negative bacilli on the body surface. Among them, 15 were infected with the same bacteria in the wound, urine, blood and lung. 6 out of 7 cases with serious infections had been colonized by Gram-negative bacilli on the surface of the whole body. Computer analysis indicated that the methods of using antibiotic should be improved. In summary, preserving adequate anti-infection immunity and effective control of rejection is the key point of this study.

Bacterial Infections↗
PubMed1990

Import of the iron-sulfur protein of the cytochrome b.c1 complex into yeast mitochondria.

The yeast gene for the Rieske iron-sulfur protein of the cytochrome b.c1 complex was subcloned into the expression vector, pSP64, then transcribed and translated in vitro in a reticulocyte lysate in the presence of [35S]methionine. Import studies in vitro of the newly synthesized precursor form of the iron-sulfur protein into isolated yeast mitochondria revealed that the precursor form of the iron-sulfur protein is processed into the mature form via an intermediate form. After the import reaction at 18 or 27 degrees C, treatment of mitochondria with exogenous protease indicated that both intermediate and mature forms had been internalized into mitochondria where they were resistant to digestion by external protease. Import and processing of the iron-sulfur protein into mitochondria also occurred at temperatures ranging from 2 to 27 degrees C in a temperature-dependent manner. Processing of the precursor form to the intermediate form appeared to be less sensitive to temperature than the processing of the intermediate form to the mature form. Moreover, at temperatures of 12 degrees C or lower, the mature form produced was completely digested by exogenous protease suggesting that it was assembled incorrectly in the membrane and not assembled into the b.c1 complex. The successive disappearance of first the mature form and then the intermediate form of the iron-sulfur protein by increasing concentrations of the metal chelators, EDTA and o-phenanthroline, suggested that two different proteases requiring divalent metal ions are involved in the two-step processing of the presequence of the iron-sulfur protein. Furthermore, mitoplasts containing only the matrix/inner membrane fraction were able to import and process the precursor form of the iron-sulfur protein indicating that both proteolytic processing events occur in the matrix/inner membrane fraction.

Electron Transport Complex III↗
PubMed1990

[Change of myocardial glucose and free fatty acid metabolism and effect of electroacupuncture on them during experimental myocardial angina].

This study was designed to observe the effect of electroacupuncture applied at "Neiguan" point on myocardial Glucose (GLU) and Free fatty acid (FFA) metabolism of dogs with experimental myocardial angina, experimental myocardial angina model was set up in 20 healthy mongrel dogs with reducing the volume of blood flow of left anterior descending coronary (LAD) and intracoronary administration of bradykinin. The results showed that arterial-venous difference of glucose (GLUa-v) was increased significantly and arterial-venous difference of free fatty acid (FFAa-v) was decreased significantly after experimental myocardial angina. with prolongation of the period of myocardial ischemia and increase of the times of myocardial angina, in control group, GLUa-v was increased lightly and FFAa-v was markedly decreased (P less than 0.05), this showed that FFA uptake of ischemic myocardium was markedly decreased. Electroacupuncture at bilateral "Neiguan" point resulted significant decrease of GLUa-v and slight increase of FFAa-v. There were statistical significance between the two groups (P less than 0.05) in GLUa-v and FFA-v. Aterial blood free fatty acid had not significant change after experimental myocardial angina and electroacupuncture had not marked effect on it. The above results indicated that experimental myocardial angina result in metabolic disorders of myocardial glucose and free fatty acid. Electroacupuncture may reduce glucose uptake and increase free fatty acid uptake of ischemic myocardium. Thus improved metabolic disorder of ischemic myocardium.

Acupuncture Therapy↗
PubMed1976

Structural aberrations of the long arm of chromosome no. 22. Report fo a family with translocation t(11;22) (q25;q11).

A chromosomal translocation t(11;22) (q25q11) is described in a family. Four members, in two generations, had the same translocation but showed phenotypic variation. Case reports of chromosome aberrations involving the long arm of chromosome 22 associated with and without chronic myeloid leukemia (CML) are reviewed. It appears that the distal segment of the long arm or chromosome 22 is either translocated or deleted, resulting in congenital anomalies, presumably due to chromosome imbalance. In other instances, a specific breakpoint on 22q results in the origin of Philadelphia chromosome (Ph1) associated with CML.

Abnormalities, Multiple↗
PubMedDate not supplied

The catalytic subunit of telomerase is expressed in developing brain neurons and serves a cell survival-promoting function.

Telomerase, a specialized reverse transcriptase (RT) linked to cell immortalization and cancer, has been thought not to be expressed in postmitotic cells. We now report that telomerase activity and its essential catalytic subunit, telomerase reverse transcriptase (TERT), are expressed in neurons in the brains of rodents during embryonic and early postnatal development, and are subsequently downregulated. Suppression of TERT expression in cultured embryonic hippocampal neurons increases their vulnerability to apoptosis and excitotoxicity. Overexpression of TERT in PC12 cells suppresses apoptosis induced by trophic factor withdrawal. TERT exerts its anti-apoptotic action at an early stage of the cell death process prior to mitochondrial dysfunction and caspase activation. TERT may serve a neuron survival-promoting function in the developing brain, and downregulation of TERT in the adult brain may contribute to increased neuronal vulnerability in various age-related neurodegenerative disorders.

Aging↗