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Teixeira M, Meleiro C. A new method for analysis of plasma carotenoids in poultry. ARQ BRAS MED VET ZOO 2008. [DOI: 10.1590/s0102-09352008000600014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A study was carried out to evaluate a new quantitative analytical technique for determination of plasma carotenoids in poultry. Plasma carotenoides were extracted and measured from 30 blood samples of male Cobb broilers. The new technique was efficient in detecting plasma carotenoids of chickens and also showed advantages upon those techniques currently in use such as the form of presentation of results, use of a compatible solvent, and the scanning method for reading. The new technique did not increase the cost of the analysis.
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Oliveira-Montanaro S, de Arruda H, Sugimoto É, Teixeira M, Bavaresco M, Alves K, Oliveira L. SCHU-09: Benign Prostatic Hyperplasia (BPH) and Prostatic Cancer (PC) Aminopeptidasis. Urology 2008. [DOI: 10.1016/j.urology.2008.08.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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78
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Teixeira M, Afonso CMM, Pinto MMM, Barbosa CM. Development and Validation of an HPLC Method for the Quantitation of 1,3-Dihydroxy-2-methylxanthone in Biodegradable Nanoparticles. J Chromatogr Sci 2008; 46:472-8. [DOI: 10.1093/chromsci/46.6.472] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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79
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Antunes M, Oliveira M, Teixeira M, Veloso A, Veloso F, Panagopoulos T. EVALUATION OF THE EFFECT OF COMPLEMENTARY POLLINATION ON ACTINIDIA DELICIOSA 'HAYWARD' IN NORTHWEST PORTUGAL. ACTA ACUST UNITED AC 2007. [DOI: 10.17660/actahortic.2007.753.43] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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80
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Teixeira M, Silva E, Selores M. Acute generalized exanthematous pustulosis induced by nimesulide. Dermatol Online J 2006; 12:20. [PMID: 17083900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023] Open
Abstract
Nimesulide is a new nonsteroidal anti-inflammatory (NSAID) drug with antipyretic and analgesic properties. Because of its favorable tolerability profile it appears to be a preferred alternative, especially in NSAID-sensitive patients. We report a case of acute generalized exanthematous pustulosis (AGEP) in a 50-year-old woman that was attributed to the ingestion of nimesulide. To the best of our knowledge there have been no previous reports of AGEP induced by the ingestion of nimesulide in the medical literature. Nimesulide should be added to the list of agents associated with this serious adverse drug reaction.
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Martins L, Pedroso S, Henriques AC, Dias L, Sarmento AM, Seca R, Oliveira F, Dores J, Lhamas A, Coelho T, Ribeiro A, Esteves S, Pereira R, Almeida R, Amil M, Cabrita A, Teixeira M. Simultaneous Pancreas-Kidney Transplantation: Five-Year Results From a Single Center. Transplant Proc 2006; 38:1929-32. [PMID: 16908326 DOI: 10.1016/j.transproceed.2006.06.089] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
We report the 5-year results of our simultaneous pancreas-kidney transplantation (SPKT) program, started on May 2, 2000. Forty-two SPKT were performed on 42 type I diabetic patients with chronic renal failure. The procedure was performed with enteric diversion and vascular anastomosis to the iliac vessels. Immunosuppressive protocol included antithymocyte globulin, tacrolimus, mycophenolate mofetil, and steroids. The 24 women and 18 men had a mean age of 33.5 +/- 6.3 years and mean 22.8 +/- 14.2 years time of diabetes evolution. Forty patients had been on dialysis for 34.3 +/- 24.1 months, and two were preemptive transplantations. Acute rejection episodes were treated in eight patients (19.1%): in three cases they affected both organs; in two only the kidney was affected; and the other three were pancreas graft rejections. The incidence of postoperative complications requiring re-operation was 42.9%, mostly pancreas graft related. Two patients died, one due to cardiovascular disease; the other was transplant related. Three kidney grafts were lost, and the causes were immunologic, thrombosis, and patient death. Pancreas graft loss occurred in seven patients: thrombosis (n = 3); infection (n = 3); immunologic (n = 1). The patients with surviving grafts were doing well, with normal kidney and pancreas function: serum creatinine = 0.89 +/- 0.15 mg/dL; fasting blood glucose = 79 +/- 16 mg/dL; HbA1c = 4.7 +/- 1.1%. The 1-year patient, kidney, and pancreas survival rates were 97.3%, 94.6%, and 83.8% and 5-year values, 91.7%, 89.2%, and 78.7%, respectively. In conclusion, these results are similar to the most recent UNOS/IPTR reports, leading us to consider our experience with SPKT very positive.
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82
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Carmo M, Faria TQ, Falk H, Coroadinha AS, Teixeira M, Merten OW, Gény-Fiamma C, Alves PM, Danos O, Panet A, Carrondo MJT, Cruz PE. Relationship between retroviral vector membrane and vector stability. J Gen Virol 2006; 87:1349-1356. [PMID: 16603538 DOI: 10.1099/vir.0.81302-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The present work studies the physico-chemical properties of retroviral vector membrane, in order to provide some explanation for the inactivation kinetics of these vectors and to devise new ways of improving transduction efficiency. For this purpose, vectors with an amphotropic envelope produced by TE Fly A7 cells at two culture temperatures (37 and 32 °C) were characterized by different techniques. Electron paramagnetic resonance (EPR) results showed that vectors produced at 32 °C are more rigid than those produced at 37 °C. Further characterization of vector membrane composition allowed us to conclude that the vector inactivation rate increases with elevated cholesterol to phospholipid ratio. Differential scanning calorimetry (DSC) showed that production temperature also affects the conformation of the membrane proteins. Transduction studies using HCT116 cells and tri-dimensional organ cultures of mouse skin showed that vectors produced at 37 °C have higher stability and thus higher transduction efficiency in gene therapy relevant cells as compared with vectors produced at 32 °C. Overall, vectors produced at 37 °C show an increased stability at temperatures below 4 °C. Since vector membrane physico-chemical properties are affected in response to changes in culture temperature, such changes, along with alterations in medium composition, can be used prospectively to improve the stability and the transduction efficiency of retroviral vectors for therapeutic purposes.
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83
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Teixeira M, Silva E, Selores M. Acute generalized exanthematous pustulosis induced by nimesulide. Dermatol Online J 2006. [DOI: 10.5070/d39jh591qq] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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84
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Archer M, Brito J, Bandeiras TM, Teixeira M. Structure of NADH: quinone oxidoreductase from Acidianus ambivalens: electron entry point of aerobic respiratory chain. Acta Crystallogr A 2005. [DOI: 10.1107/s0108767305090367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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85
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Araujo A, Teixeira M, Figueiredo A, Correia J, Melo M, Parente B, Bernardo M, Queiroga H, Barata F. P-447 Treatment of non-small-cell lung cancer with gefitinib (IRESSA)in a compassionate-use program: The Portuguese experience. Lung Cancer 2005. [DOI: 10.1016/s0169-5002(05)80940-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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86
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Soares AC, Souza DG, Pinho V, Vieira AT, Barsante MM, Nicoli JR, Teixeira M. Impaired host defense to Klebsiella pneumoniae infection in mice treated with the PDE4 inhibitor rolipram. Br J Pharmacol 2004; 140:855-62. [PMID: 14585803 PMCID: PMC1574107 DOI: 10.1038/sj.bjp.0705517] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The increase in levels of cAMP in leukocytes by selective inhibitors of PDE4 may result in reduction of inflammation, and may be useful in the treatment of pulmonary inflammatory disorders in humans. Here, we have assessed whether oral treatment with the prototype PDE4 inhibitor, rolipram, interfered with the antibacterial host response following pulmonary infection of mice with Klebsiella pneumoniae. K. pneumoniae infection induced a marked increase in the recruitment of neutrophils to the lungs and the production of proinflammatory cytokines and chemokines, including tumor necrosis factor-alpha (TNF-alpha) and keratinocyte-derived chemokine (KC), in bronchoalveolar (BAL) fluid and lung tissue. There were also detectable amounts of interleukin-10 (IL-10) and significant lethality. Treatment with rolipram (3-30 mg kg-1) was associated with earlier lethality and significant inhibition of the TNF-alpha production. This was associated with enhanced production of IL-10 in lung tissue of rolipram-treated animals. Rolipram treatment did not affect KC expression and the recruitment of neutrophils in the lung tissue. Over 70% of neutrophils that migrated into the BAL fluid following K. pneumoniae infection ingested bacteria. Treatment with rolipram inhibited the percentage of neutrophils undergoing phagocytosis of K. pneumoniae in a dose-dependent manner. Maximal inhibition (62%) occurred at doses equal to or greater than 10 mg kg-1. Thus, treatment of mice with the PDE4 inhibitor rolipram is accompanied by earlier lethality, enhanced bacterial load and decreased capacity of the responding host to produce TNF-alpha and of neutrophils to phagocytose bacteria. It will be important to investigate whether the shown ability of PDE4 inhibitors to inhibit neutrophil phagocytosis and control experimental bacterial infection will translate into an inhibition of the ability of neutrophils to deal with infectious microorganisms in the clinical setting.
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87
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Teixeira M, Teixeira Filho WL, Lopes CWG. Coccidiosis in japanese quails (Coturnix japonica): characterization of a naturally occurring infection in a commercial rearing farm . BRAZILIAN JOURNAL OF POULTRY SCIENCE 2004. [DOI: 10.1590/s1516-635x2004000200010] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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88
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Teixeira M, Pinto MMM, Barbosa CM. Validation of a spectrophotometric method for quantification of xanthone in biodegradable nanoparticles. DIE PHARMAZIE 2004; 59:257-9. [PMID: 15125567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
Xanthone has been incorporated for the first time in nanoparticles of poly(D,L-lactide-co-glycolide) (PLGA). For this purpose the estimation of xanthone content in the nanoparticles is a crucial tool for guaranteeing the reliability of the results. Thus, a simple spectrophotometric method was validated according to USP25 and ICH guidelines for its specificity, linearity, accuracy and precision. The method was found to be specific for xanthone in the presence of nanoparticle excipients. The calibration curve was linear over the concentration range of 0.5 to 4.0 microg/mL (r > 0.999). Recovery of xanthone from nanoparticles ranged from 86.5 to 95.9%. Repeatability (intra-assay precision) and intermediate precision were found to be acceptable with relative standard deviations values (RSD) ranging from 0.3 to 3.0% and from 1.4 to 3.1%, respectively. The method was found to be suitable for the evaluation of xanthone content in nanoparticles of PLGA.
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89
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Sarti P, Fiori PL, Forte E, Rappelli P, Teixeira M, Mastronicola D, Sanciu G, Giuffré A, Brunori M. Trichomonas vaginalis degrades nitric oxide and expresses a flavorubredoxin-like protein: a new pathogenic mechanism? Cell Mol Life Sci 2004; 61:618-623. [PMID: 15004700 PMCID: PMC11146037 DOI: 10.1007/s00018-003-3413-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Besides possessing many physiological roles, nitric oxide (NO) produced by the immune system in infectious diseases has antimicrobial effects. Trichomoniasis, the most widespread non-viral sexually transmitted disease caused by the microaerophilic protist Trichomonas vaginalis, often evolves into a chronic infection, with the parasite able to survive in the microaerobic, NO-enriched vaginal environment. We relate this property to the finding that T. vaginalis degrades NO under anaerobic conditions, as assessed amperometrically. This activity, which is maximal (133 +/- 41 nmol NO/10(8) cells per minute at 20 degrees C) at low NO concentrations (< or = 1.2 microM), was found to be: (i) NADH dependent, (ii) cyanide insensitive and (iii) inhibited by O(2). These features are consistent with those of the Escherichia coli A-type flavoprotein (ATF), recently discovered to be endowed with NO reductase activity. Using antibodies against the ATF from E. coli, a protein band was immunodetected in the parasite grown in a standard medium. If confirmed, the expression of an ATF in eukaryotes suggests that the genes coding for ATFs were transferred during evolution from anaerobic Prokarya to pathogenic protists, to increase their fitness for the microaerobic, parasitic life style. Thus the demonstration of an ATF in T. vaginalis would appear relevant to both pathology and evolutionary biology. Interestingly, genomic analysis has recently demonstrated that Giardia intestinalis and other pathogenic protists have genes coding for ATFs.
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90
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Martins L, Henriques A, Dias L, Ventura A, Seca R, Almeida R, Dores J, Bacelar C, Oliveira F, Lhamas A, Amil M, Rua F, Coelho T, Esteves S, Ribeiro A, Pereira R, Sarmento A, Teixeira M, Pereira M. Combined pancreas-kidney transplantation: a new program in Portugal, results from the first 12 cases. Transplant Proc 2003; 35:1107-8. [PMID: 12947877 DOI: 10.1016/s0041-1345(03)00327-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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91
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Lobato L, Ventura A, Beirão I, Miranda HP, Seca R, Henriques AC, Teixeira M, Sarmento AM, Pereira MC. End-stage renal disease in familial amyloidosis ATTR Val30Met: a definitive indication to combined liver-kidney transplantation. Transplant Proc 2003; 35:1116-20. [PMID: 12947881 DOI: 10.1016/s0041-1345(03)00331-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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92
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Laurell G, Teixeira M, Sterkers O, Bagger-Sjöbäck D, Eksborg S, Lidman O, Ferrary E. Local administration of antioxidants to the inner ear. Kinetics and distribution(1). Hear Res 2002; 173:198-209. [PMID: 12372647 DOI: 10.1016/s0378-5955(02)00613-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Round window (r.w.) administration of drugs involves the delivery of medication directly into the inner ear via the r.w. membrane, avoiding a systemic effect of the therapy. Earlier experimental studies suggest that a number of antioxidants and scavengers hold promise for ameliorating the tissue damaging capacity of reactive oxygen species in some acquired cochlear disorders. D-Methionine and thiourea are two small sulfur-containing molecules with an antioxidative and scavenging effect. The passage through the r.w. of radioactive D-methionine and thiourea administered by 1 h infusion to the r.w. was studied in a rat model. Levels of the tracers were measured in scala tympani perilymph (PLT) 17-254 min after r.w. administration. Both tracers pass the r.w. membrane readily. Peak levels were found in the earliest taken samples after the administration. The radioactivity in PLT of the basal turn reached a peak to about 1.5-1.9% of the irrigating medium radioactivity. Following the r.w. administration, the concentration of radioactive D-methionine and thiourea declined with a terminal half-life of 0.57 and 0.77 h, respectively. The distribution of the tracers at the cellular level was analyzed by autoradiography. The most intense expression was found in the lateral wall of the cochlea. It can be postulated that local delivery to the cochlea of D-methionine and thiourea via the r.w. gives high local concentrations of the substances in PLT in the basal turn.
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93
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Shafey O, Cokkinides V, Cavalcante TM, Teixeira M, Vianna C, Thun M. Case studies in international tobacco surveillance: cigarette smuggling in Brazil. Tob Control 2002; 11:215-9. [PMID: 12198271 PMCID: PMC1759007 DOI: 10.1136/tc.11.3.215] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
OBJECTIVE This article is the first in a series of international case studies developed by the American Cancer Society to illustrate use of publicly available surveillance data for regional tobacco control. DESIGN A descriptive analysis of Brazil and Paraguay cigarette production and trade data from official sources. METHODS Per capita cigarette consumption for Brazil and its neighbour was calculated from 1970 to 1998 using data on production, imports, and exports from NATIONS, the National Tobacco Information Online System. RESULTS A 63% decrease was observed in the estimate of per capita consumption of cigarettes in Brazil between 1986 and 1998 (from 1913 cigarettes per person in 1986 to 714 cigarettes per person in 1998) and a 16-fold increase in Paraguay was observed during the same period (from 678 cigarettes per person in 1986 to 10 929 cigarettes per person in 1998). Following Brazil's 1999 passage of a 150% cigarette export tax, cigarette exports fell 89% and Brazil's estimated per capita consumption rose to 1990 levels (based on preliminary data). Per capita consumption in Paraguay also fell to 1990 levels. CONCLUSIONS These trends coincide with local evidence that large volumes of cigarettes manufactured in Brazil for export to Paraguay are smuggled back and consumed as tax-free contraband in Brazil. It is hoped that this case study will draw wider public attention to the problems that smuggling presents for tobacco control, help identify other countries confronting similar issues, and stimulate effective interventions.
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94
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Macedo S, Mitchell EP, Matias PM, Romao CV, Liu MY, Xavier AV, Lindley PF, Le Gall J, Teixeira M, Carrondo MA. Bacterioferritin from Desulfovibrio desulfuricans: the identification of the ferroxidase centre. Acta Crystallogr A 2002. [DOI: 10.1107/s0108767302089766] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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95
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Lindley PF, Aragao DG, Macedo S, Frazao C, Mitchell E, Romao CV, Teixeira M, Hagen WR, Carrondo MA. Hybrid cluster protein (HCP) from Desulfovibrio vulgarisand Desulfovibrio desulfuricans: aerobic, anaerobic and reduced structural studies. Acta Crystallogr A 2002. [DOI: 10.1107/s0108767302094886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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96
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Aragao DG, Macedo S, Frazao C, Mitchell E, Romao C, Teixeira M, Hagen WR, Carrondo MA, Lindley P. Hybrid cluster protein (HCP) from Desulfovibrio vulgarisand Desulfovibrio desulfuricans: aerobic, anaerobic and reduced structural studies. Acta Crystallogr A 2002. [DOI: 10.1107/s0108767302089699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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97
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Valente FM, Saraiva LM, LeGall J, Xavier AV, Teixeira M, Pereira IA. A membrane-bound cytochrome c3: a type II cytochrome c3 from Desulfovibrio vulgaris Hildenborough. Chembiochem 2001; 2:895-905. [PMID: 11948878 DOI: 10.1002/1439-7633(20011203)2:12<895::aid-cbic895>3.0.co;2-v] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A new tetraheme cytochrome c3 was isolated from the membranes of Desulfovibrio vulgaris Hildenborough (DvH). This cytochrome has a molecular mass of 13.4 kDa and a pI of 5.5 and contains four heme c groups with apparent reduction potentials of -170 mV, -235 mV, -260 mV and -325 mV at pH 7.6. The complete sequence of the new cytochrome, retrieved from the preliminary data of the DvH genome, shows that this cytochrome is homologous to the "acidic" cytochrome c3 from Desulfovibrio africanus (Da). A model for the structure of the DvH cytochrome was built based on the structure of the Da cytochrome. Both cytochromes share structural features that distinguish them from other cytochrome c3 proteins, such as a solvent-exposed heme 1 surrounded by an acidic surface area, and a heme 4 which lacks most of the surface lysine patch proposed to be the site of hydrogenase interaction in other cytochrome c3 proteins. Furthermore, in contrast to previously discovered cytochrome c3 proteins, the genes coding for these two cytochromes are adjacent to genes coding for two membrane-associated FeS proteins, which indicates that they may be part of membrane-bound oxidoreductase complexes. Altogether these observations suggest that the DvH and Da cytochromes are a new type of cytochrome c3 proteins (Type II: TpII-c3) with different redox partners and physiological function than the other cytochrome c3 proteins (Type I: TpI-c3). The DvH TpII-c3 is reduced at considerable rates by the two membrane-bound [NiFe] and [NiFeSe] hydrogenases, but catalytic amounts of TpI-c3 increase these rates two- and fourfold, respectively. With the periplasmic [Fe] hydrogenase TpII-c3 is reduced much slower than TpI-c3, and no catalytic effect of TpI-c3 is observed.
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98
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Abreu IA, Saraiva LM, Soares CM, Teixeira M, Cabelli DE. The mechanism of superoxide scavenging by Archaeoglobus fulgidus neelaredoxin. J Biol Chem 2001; 276:38995-9001. [PMID: 11489883 DOI: 10.1074/jbc.m103232200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neelaredoxin is a mononuclear iron protein widespread among prokaryotic anaerobes and facultative aerobes, including human pathogens. It has superoxide scavenging activity, but the exact mechanism by which this process occurs has been controversial. In this report, we present the study of the reaction of superoxide with the reduced form of neelaredoxin from the hyperthermophilic archaeon Archaeoglobus fulgidus by pulse radiolysis. This protein reduces superoxide very efficiently (k = 1.5 x 10(9) m(-1)s(-1)), and the dismutation activity is rate-limited, in steady-state conditions, by the much slower superoxide oxidation step. These data show unambiguously that the superfamily of neelaredoxin-like proteins (including desulfoferrodoxin) presents a novel type of reactivity toward superoxide, a result of particular relevance for the understanding of both oxygen stress response mechanisms and, in particular, how pathogens may respond to the oxidative burst produced by the defense cells in eukaryotes. The actual in vivo functioning of these enzymes will depend strongly on the cell redox status. Further insight on the catalytic mechanism was obtained by the detection of a transient intermediate ferric species upon oxidation of neelaredoxin by superoxide, detectable by visible spectroscopy with an absorption maximum at 610 nm, blue-shifted approximately 50 nm from the absorption of the resting ferric state. The role of the iron sixth ligand, glutamate-12, in the reactivity of neelaredoxin toward superoxide was assessed by studying two site-directed mutants: E12Q and E12V.
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Janssen S, Trincão J, Teixeira M, Schäfer G, Anemüller S. Ferredoxins from the archaeon Acidianus ambivalens: overexpression and characterization of the non-zinc-containing ferredoxin FdB. Biol Chem 2001; 382:1501-7. [PMID: 11727834 DOI: 10.1515/bc.2001.184] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Two ferredoxin genes, fdA and fdB, from the extremely thermoacidophilic crenarchaeon Acidianus ambivalens have been sequenced; the sequences share 86% similarity. Whereas the deduced protein sequence of the ferredoxin FdA clearly contains a zinc-binding motif, the corresponding sequence of the FdB is devoid of this motif. Thus far, only the zinc-containing ferredoxin, FdA, from A. ambivalens has been chemically and functionally characterized from its native source. Using RT-PCR and Northern blot analysis, we show that both ferredoxins are expressed by A. ambivalens under either anaerobic or aerobic growth conditions. The zinc-free ferredoxin, FdB, was overexpressed in E. coli and purified to homogeneity. Using EPR spectroscopy, we could demonstrate that FdB contains one [3Fe-4S](1+/0) and one [4Fe-4S](2+/1+) cluster. The reduction potential of the [3Fe-4S](1+/0) cluster was determined as -235+/-10 mV, at pH 6.5, by EPR-monitored redox titration. The high melting temperature of 108+/-2 degrees C of FdB determined by CD spectroscopy reveals that it is not the binding of the Zn2+ that induces the extreme thermostability of these ferredoxins.
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100
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Sigurdson H, Namslauer A, Pereira MM, Teixeira M, Brzezinski P. Ligand binding and the catalytic reaction of cytochrome caa(3) from the thermophilic bacterium Rhodothermus marinus. Biochemistry 2001; 40:10578-85. [PMID: 11524000 DOI: 10.1021/bi010344h] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The ligand-binding dynamics and the reaction with O(2) of the fully (five-electron) reduced cytochrome caa(3) from the thermohalophilic bacterium Rhodothermus (R.) marinus were investigated. The enzyme is a proton pump which has all the residues of the proton-transfer pathways found in the mitochondrial-like enzymes conserved, except for one of the key elements of the D-pathway, the helix-VI glutamate [Glu(I-286), R. sphaeroides numbering]. In contrast to what has been suggested previously as general characteristics of thermophilic enzymes, during formation of the R. marinus caa(3)-CO complex, CO binds weakly to Cu(B), and is rapidly (k(Ba) = 450 s(-1)) trapped by irreversible (K(Ba) = 4.5 x 10(3)) binding to heme a(3). Upon reaction of the fully reduced enzyme with O(2), four kinetic phases were resolved during the first 10 ms after initiation of the reaction. On the basis of a comparison to reactions observed with the bovine enzyme, these phases were attributed to the following transitions between intermediates (pH 7.8, 1 mM O(2)): R --> A (tau congruent with 8 micros), A --> P(r) (tau congruent with 35 micros), P(r) --> F (tau congruent with 240 micros), F --> O (tau congruent with 2.5 ms), where the last two phases were associated with proton uptake from the bulk solution. Oxidation of heme c was observed only during the last two reaction steps. The slower transition times as compared to those observed with the bovine enzyme most likely reflect the replacement of Glu(I-286) of the helix-VI motif -XGHPEV- by a tyrosine in the R. marinus enzyme in the motif -YSHPXV-. The presence of an additional, fifth electron in the enzyme was reflected by two additional kinetic phases with time constants of approximately 20 and approximately 720 ms during which the fifth electron reequilibrated within the enzyme.
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