155 research outputs found
Membrane-associated cytochrome c(y) of Rhodobacter capsulatus is an electron carrier from the cytochrome bc1 complex to the cytochrome c oxidase during respiration
No full textWe have recently established that the facultative phototrophic bacterium Rhodobacter capsulatus has two different pathways for reduction of the photooxidized reaction center during photosynthesis (F. E. Jenney and F. Daldal, EMBO J. 12:1283-1292, 1993; F. E. Jenney, R. C. Prince, and F. Daldal, Biochemistry 33:2496-2502, 1994). One pathway is via the well- characterized, water-soluble cytochrome c2 (cyt c2), and the other is via a novel membrane-associated c-type cytochrome named cyt c(y). In this work, we probed the role of cyt c(y) in respiratory electron transport by isolating a set of R. capsulatus mutants lacking either cyt c2 or cyt c(y), in the presence or in the absence of a functional quinol oxidase-dependent alternate respiratory pathway. The growth and inhibitor sensitivity patterns of these mutants, their respiratory rates in the presence of specific inhibitors, and the oxidation-reduction kinetics of c-type cytochromes monitored under appropriate conditions demonstrated that cyt c(y), like cyt c2, connects the Bc1 complex and the cyt c oxidase during respiratory electron transport. Whether cyt c2 and cyt c(y) are the only electron carriers between these two energy-transducing membrane complexes of R. capsulatus is unknown
Roles of the soluble cytochrome c2 and membrane-associated cytochrome cy of rhodobacter capsulatus in photosynthetic electron transfer
No full textGenetic evidence indicates that Rhodobacter capsulatus has two different pathways for reduction of the photooxidized reaction center (RC) [Jenney, F. E., & Daldal, F. (1993) EMBOJ. 12, 1283-1292]. One pathway is via the water soluble cytochrome (cyt) c2, and the other is via a novel, membrane-associated c-type cytochrome, cyt cy, now believed to be identical to the cyt cx of Jones et al. [Jones, M. R., et al. (1990) Biochim. Biophys. Acta 975, 59-66] and c354 of Zannoni et al. [Zannoni, D., et al. (1992) Arch. Microbiol. 157, 367-374]. Mutants lacking either cyt c2, cyt cy, or the bc1 complex, as well as various combinations, were utilized to probe the functional role of these cytochromes in electron transfer. Data obtained by monitoring flash induced electron transfer kinetics in the RC, cyt c pool, cyt b, and the carotenoid band shift indicate that there are two pathways for electron transfer from the bc1 complex to the RC in R. capsulatus, one via cyt c2 and the other through cyt cy. The two pathways show strikingly different kinetics for RC reduction and cyt c oxidation, and both are present in the wild-type strain MT-1131. After genetic inactivation of both cyt c2 and cyt cy there remains no flash oxidizible c-type cytochrome, and inactivation of cyt cy rather than cyt c2 has a more pronounced effect on the extent of the light-induced membrane potential under the conditions tested. Finally, heme-stained SDS-PAGE and flash spectroscopy experiments indicate that cyt cy is detectable in strains lacking the bc1 complex when grown on minimal growth medium but not on rich medium. These findings complement the earlier genetic data and further establish that cyt cy is the electron carrier permitting soluble cyt c2-independent photosynthetic growth in R. capsulatus. © 1994 American Chemical Society
The membrane-bound cytochrome cy of Rhodobacter capsulatus can serve as an electron donor to the photosynthetic reaction center of Rhodobacter sphaeroides
No full textAbstractRhodobacter capsulatus has two different pathways for reduction of the photo-oxidized reaction center, one using water-soluble cytochrome c2, the other via membrane-associated cytochrome cy. Rhodobacter sphaeroides differs in that it lacks a cytochrome cy homologue capable of functioning in photosynthetic electron transfer; cytochrome c2 is thus the sole electron carrier, and is required for photosynthetic (Ps+) growth. Genetic evidence indicates that cytochrome cy of R. capsulatus can complement a Ps− cytochrome-c2-deficient mutant of R. sphaeroides (Jenney, F.E. and Daldal, F. (1993) EMBO J. 12, 1283–1292). Here, we show that is transfers electrons from the cytochrome bc1 complex to the reaction center in R. sphaeroides, albeit at a lower rate than that catalyzed by the endogenous cytochrome c2. When cytochrome cy is expressed in R. sphaeroides in the presence of cytochrome c2, there is an increase in the amount of photo-oxidizible c-type cytochrome. In the absence of cytochrome c2, electron transfer via cytochrome cy shows significantly different kinetics for reaction center reduction and cytochrome c oxidation. These findings further establish that cytochrome cy, the electron carrier permitting soluble cytochrome c2-independent photosynthetic growth in R. capsulatus, can function in a similar capacity in R. sphaeroides
Solvent Tuning of Electrochemical Potentials in the Active Sites of HiPIP Versus Ferredoxin
No full textA persistent puzzle in the field of biological electron transfer is the conserved iron-sulfur cluster motif in both high potential iron-sulfur protein (HiPIP) and ferredoxin (Fd) active sites. Despite this structural similarity, HiPIPs react oxidatively at physiological potentials, whereas Fds are reduced. Sulfur K-edge x-ray absorption spectroscopy uncovers the substantial influence of hydration on this variation in reactivity. Fe-S covalency is much lower in natively hydrated Fd active sites than in HiPIPs but increases upon water removal; similarly, HiPIP covalency decreases when unfolding exposes an otherwise hydrophobically shielded active site to water. Studies on model compounds and accompanying density functional theory calculations support a correlation of Fe-S covalency with ease of oxidation and therefore suggest that hydration accounts for most of the difference between Fd and HiPIP reduction potentials
Auger holes through the Original Big Tree showing means by which it was felled
No full textPart of Mammoth Tree series.No. 13.Title from item.Gift; Frederick G. Jenney; 1959
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Having Your Yellow Cake and Eating It Too: The Environmental and Health Impacts of Uranium Mining on the Colorado Plateau
No full textOn May 6th, 2011, the Ninth Circuit upheld the Arizona District Court’s ruling in Ctr. for Biological Diversity v. Salazar. The court determined that pursuant to current Environmental Protection Agency (EPA) regulations, the Bureau of Land Management (BLM) was not required to review and approve a new plan of operations to allow mining activities at a uranium mine on the Colorado Plateau that had been dormant for almost twenty years. The court held that reopening the mine and acquiring the necessary permits did not constitute a major action, therefore not requiring a new plan of operations to be submitted to the BLM for review and approval pursuant to the National Environmental Policy Act (NEPA). This article agrees with the Ninth Circuit that, under NEPA regulations, no new environmental impact statement was needed. However, this article contends that NEPA regulations requiring certain safety precautions and environmental assessments be undertaken by uranium mines prior to the commencement of mining activities must be rewritten to further protect the environment as well as the health of the people that call the Colorado Plateau home.This material published in Arizona Journal of Environmental Law & Policy is made available by the James E. Rogers College of Law, the Daniel F. Cracchiolo Law Library, and the University of Arizona Libraries. If you have questions, please contact the AJELP Editorial Board at https://ajelp.com/contact-us
Structures of the Superoxide Reductase from Pyrococcus furiosus in the Oxidized and Reduced States
No full textSuperoxide reductase (SOR) is a blue non-heme iron protein that functions in anaerobic microbes as a defense mechanism against reactive oxygen species by catalyzing the reduction of superoxide to hydrogen peroxide [Jenney, F. E., Jr., Verhagen, M. F. J. M., Cui, X., and Adams, M. W. W. (1999) Science 286, 306−309]. Crystal structures of SOR from the hyperthermophilic archaeon Pyrococcus furiosus have been determined in the oxidized and reduced forms to resolutions of 1.7 and 2.0 Å, respectively. SOR forms a homotetramer, with each subunit adopting an immunoglobulin-like β-barrel fold that coordinates a mononuclear, non-heme iron center. The protein fold and metal center are similar to those observed previously for the homologous protein desulfoferrodoxin from Desulfovibrio desulfuricans [Coelho, A. V., Matias, P., Fülöp, V., Thompson, A., Gonzalez, A., and Carrondo, M. A. (1997) J. Bioinorg. Chem. 2, 680−689]. Each iron is coordinated to imidazole nitrogens of four histidines in a planar arrangement, with a cysteine ligand occupying an axial position normal to this plane. In two of the subunits of the oxidized structure, a glutamate carboxylate serves as the sixth ligand to form an overall six-coordinate, octahedral coordinate environment. In the remaining two subunits, the sixth coordination site is either vacant or occupied by solvent molecules. The iron centers in all four subunits of the reduced structure exhibit pentacoordination. The structures of the oxidized and reduced forms of SOR suggest a mechanism by which superoxide accessibility may be controlled and define a possible binding site for rubredoxin, the likely physiological electron donor to SOR
Automation Applications in an Advanced Air Traffic Management System : Volume 4B. Automation Requirements (Concluded)
No full textDOT-TSC-512Volume 4 describes the automation requirements. A presentation of automation requirements is made for an advanced air traffic management system in terms of controller work for-e, computer resources, controller productivity, system manning, failure effects, and control/display requirements. It also includes a discussion of the application of the study results to the design and development of AATMS. Volume 4A includes Sections 1.0 through 4.3; Volume 4B includes Sections 5.0 through Appendix C and References. (Modified author abstract
Observation of Terhertz Vibrations in Pyrococcus furiosus Rubredoxin via Impulsive Coherent Vibrational Spectroscopy and Nuclear Resonance Vibrational Spectroscopy - Interpretation by Molecular Mechanics
No full textWe have used impulsive coherent vibrational spectroscopy (ICVS) to study the Fe(S-Cys)4 site in oxidized rubredoxin (Rd) from Pyrococcus furiosus (Pf). In this experiment, a 15 fs visible laser pulse is used to coherently pump the sample to an excited electronic state, and a second \u3c10 fs pulse is used to probe the change in transmission as a function of the time delay. PfRd was observed to relax to the ground state by a single exponential decay with time constants of ∼255-275 fs. Superimposed on this relaxation are oscillations caused by coherent excitation of vibrational modes in both excited and ground electronic states. Fourier transformation reveals the frequencies of these modes. The strongest ICV mode with 570 nm excitation is the symmetric Fe-S stretching mode near 310 cm-1, compared to 313 cm-1 in the low temperature resonance Raman. If the rubredoxin is pumped at 520 nm, a set of strong bands occurs between 20 and 110 cm-1. Finally, there is a mode at ∼500 cm-1 which is similar to features near 508 cm-1 in blue Cu proteins that have been attributed to excited state vibrations. Normal mode analysis using 488 protein atoms and 558 waters gave calculated spectra that are in good agreement with previous nuclear resonance vibrational spectra (NRVS) results. The lowest frequency normal modes are identified as collective motions of the entire protein or large segments of polypeptide. Motion in these modes may affect the polar environment of the redox site and thus tune the electron transfer functions in rubredoxins. © 2006 Elsevier Inc. All rights reserved
Comparison of outcomes based on treatment algorithms for rhabdomyosarcoma of the bladder/prostate: combined results from the Children's Oncology Group, German Cooperative Soft Tissue Sarcoma Study, Italian Cooperative Group, and International Society of Pediatric Oncology Malignant Mesenchymal Tumors Committee
No full texthe purpose of this study was to determine patient characteristics and outcomes for bladder/prostate (BP) rhabdomyosarcoma (RMS) using an international cohort of prospectively treated patients comparing different treatment algorithms. Data were collected from 379 patients (1979-1998) treated on protocol; Intergroup Rhabdomyosarcoma Study, IRS-IV (n = 239 patients), International Society of Pediatric Oncology Malignant Mesenchymal Tumors (MMT) Committee MMT-84 and -89 (n = 74), Italian Cooperative Group, RMS-79 and RMS-88 Studies (n = 37) or German Cooperative Soft Tissue Sarcoma Study CWS-91 protocols (n = 29). A total of 322 (85%) patients had localized embryonal RMS (ERMS) and 27 had metastatic disease. Thirty patients (21 local disease; 9 metastatic) had nonembryonal BP RMS. Patients with localized ERMS had large tumors (64% >5 cm) that were invasive (54%) with uninvolved regional lymph nodes (N0, 93%). The 5-year failure-free survival (FFS) was 75% and the overall survival (OS) was 84%, with 89% of deaths attributed to disease. Treatment failures were usually local disease recurrence (60%). Predictors of FFS included T-stage (invasiveness), size, and histology. FFS was decreased for patients not receiving initial radiotherapy but this did not translate into a decreased OS. The 21 patients with localized nonembryonal BP RMS had a FFS and OS of 47%. The 36 patients with metastatic disease were more likely to be older and had large tumors that were invasive with alveolar histology and regional lymph node involvement. The 5-year FFS and OS were 41 and 44%, respectively. In conclusion, the majority of BP RMS patients had localized ERMS with a resultant good prognosis using current treatment algorithms. There were differences in FFS between treatment protocols but this did not result in an altered OS
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