MidA is a putative methyltransferase that is required for mitochondrial complex I function

10 páginas, 6 figuras.-- et al.Dictyostelium and human MidA are homologous proteins that belong to a family of proteins of unknown function called DUF185. Using yeast two-hybrid screening and pull-down experiments, we showed that both proteins interact with the mitochondrial complex I subunit NDUFS2. Consistent with this, Dictyostelium cells lacking MidA showed a specific defect in complex I activity, and knockdown of human MidA in HEK293T cells resulted in reduced levels of assembled complex I. These results indicate a role for MidA in complex I assembly or stability. A structural bioinformatics analysis suggested the presence of a methyltransferase domain; this was further supported by site-directed mutagenesis of specific residues from the putative catalytic site. Interestingly, this complex I deficiency in a Dictyostelium midA- mutant causes a complex phenotypic outcome, which includes phototaxis and thermotaxis defects. We found that these aspects of the phenotype are mediated by a chronic activation of AMPK, revealing a possible role of AMPK signaling in complex I cytopathology.This work was supported by grants BMC2006-00394 and BMC2009-09050 to R.E. from the Spanish Ministerio de Ciencia e Innovación; to P.R.F. from the Thyne Reid Memorial Trusts and the Australian Research Council; to A.V. and O.G. from the Spanish National Bioinformatics Institute (www.inab.org), a platform of Genome Spain; to R.G. from the Fondo de Investigaciones Sanitarias, Instituto de Salud Carlos III, Spain (PI070167) and from the Comunidad de Madrid (GEN-0269/2006). S.C. is supported by a research contract from Consejería de Educación de la Comunidad de Madrid y del Fondo Social Europeo (FSE).Peer Reviewe

Simulation of afterbody transonic flows using partially-averaged navier stokes model for turbulence

This investigation is dedicated to the elaboration of a numerical strategy to simulate accurately and at a reasonable cost the main unsteady features of high Reynolds separated flows. Within this framework, the Partially-Averaged Navier Stokes (PANS) turbulence model has been used. In this hybrid approach, the modeled-to-resolved scale ratio (the level of physical resolution) is introduced and set explicitly in the closure model of the unresolved scales which is based on the ReynoldsAveraged Navier Stokes (RANS) paradigm. The flow separation behind an axisymmetric afterbody has been simulated. The large-scale coherent structures are captured and the comparison of the results with wallpressure measurements shows that the flow physics simulated is relevant. Nevertheless, these encouraging results need to be confirmed by deeper investigations on the model behavior and its sensitivity to physical as well as numerical parameters. This step of validation is mandatory before considering an extensive use of the approach at an industrial level

Adaptive Mesh Refinement with an Automatic Hybrid RANS/LES Strategy and Overset Grids

International audienc

Plume-Induced Effects on the Near-Wake Region of a Generic Space Launcher Geometry

The near-wake flow of a generic space launcher geometry with jet is investigated experimentally in the hypersonic flow regime at Mach 6 and an unit Reynolds number of 16 · 106 by means of unsteady pressure measurements. This corresponds to an altitude of 50 km for an Ariane V-like launcher with an underexpanded nozzle flow. The investigations with a truncated ideal contoured wind tunnel model nozzle designed for Mach number of 2.65 is used to simulate the nozzle flow. The objective of this study is the characterization of the plume-induced loads on the main structural components in the near wake region during flight. A parametric study with the reservoir pressures of 11, 14, 17 and 20 bar is presented. The transducers capture the pressure signal in the radial and azimuthal direction on the base and on the surface of the nozzle. The signals are spectrally analyzed with the objective to characterize and identify unsteady flow effects in order to reduce base drag and vibrations of future space launchers. The base-pressure spectra exhibits global modes at Strouhal numbers of 0.05 to 0.06, 0.09 to 0.1 and 0.2 to 0.25, which are attributed in literature to flapping and shedding. Local modes seem to occur Locally restricted modes can be detected for the tonal disturbances in the high frequency range for transducers on the base closer to the nozzle. The increase of the reservoir pressure shows a consistent increase of the pressure fluctuation level in the base region

Rocket Wake Flow Interaction Testing in the Hot Plume Testing Facility (HPTF) Cologne

Rocket wake flows were under investigation within the Collaborative Research Centre SFB/TRR40 since the year 2009. The current paper summarizes the work conducted during its third and final funding period from 2017 to 2020. During that phase, focus was laid on establishing a new test environment at the German Aerospace Center (DLR) Cologne in order to improve the similarity of experimental rocket wake flow–jet interaction testing by utilizing hydrogen–oxygen combustion implemented into the wind tunnel model. The new facility was characterized during tests with the rocket combustor model HOC1 in static environment. The tests were conducted under relevant operating conditions to demonstrate the design's suitability. During the first wind tunnel tests, interaction of subsonic ambient flow at Mach 0.8 with a hot exhaust jet of approx. 920 K was compared to previously investigated cold plume interaction tests using pressurized air at ambient temperature. The comparison revealed significant differences in the dynamic response of the wake flow field on the different types of exhaust plume simulation