The Peripheral Stalk of Rotary ATPases

Rotary ATPases are a family of enzymes that are thought of as molecular nanomotors and are classified in three types: F, A, and V-type ATPases. Two members (F and A-type) can synthesize and hydrolyze ATP, depending on the energetic needs of the cell, while the V-type enzyme exhibits only a hydrolytic activity. The overall architecture of all these enzymes is conserved and three main sectors are distinguished: a catalytic core, a rotor and a stator or peripheral stalk. The peripheral stalks of the A and V-types are highly conserved in both structure and function, however, the F-type peripheral stalks have divergent structures. Furthermore, the peripheral stalk has other roles beyond its stator function, as evidenced by several biochemical and recent structural studies. This review describes the information regarding the organization of the peripheral stalk components of F, A, and V-ATPases, highlighting the key differences between the studied enzymes, as well as the different processes in which the structure is involved

Molecular basis of diseases caused by the mtDNA mutation m.8969G>A in the subunit a of ATP synthase

The ATP synthase which provides aerobic eukaryotes with ATP, organizes into a membrane-extrinsic catalytic domain, where ATP is generated, and a membrane-embedded FO domain that shuttles protons across the membrane. We previously identified a mutation in the mitochondrial MT-ATP6 gene (m.8969G>A) in a 14-year-old Chinese female who developed an isolated nephropathy followed by brain and muscle problems. This mutation replaces a highly conserved serine residue into asparagine at amino acid position 148 of the membrane-embedded subunit a of ATP synthase. We showed that an equivalent of this mutation in yeast (aS175N) prevents FO-mediated proton translocation. Herein we identified four first-site intragenic suppressors (aN175D, aN175K, aN175I, and aN175T), which, in light of a recently published atomic structure of yeast FO indicates that the detrimental consequences of the original mutation result from the establishment of hydrogen bonds between aN175 and a nearby glutamate residue (aE172) that was proposed to be critical for the exit of protons from the ATP synthase towards the mitochondrial matrix. Interestingly also, we found that the aS175N mutation can be suppressed by second-site suppressors (aP12S, aI171F, aI171N, aI239F, and aI200M), of which some are very distantly located (by 20-30 Å) from the original mutation. The possibility to compensate through long-range effects the aS175N mutation is an interesting observation that holds promise for the development of therapeutic molecules

Present eternity : quests of temporality in the literary production of the "extrême contemporain" in France (The Writings of Dominique Fourcade and Emmanuel Hocquard)

The term \uab extr\ueame contemporain \ubb is an expression currently used by scholars to indicate the French literary production of the last 20 years. This term was used in a work of literature for the first time by the French poet Dominique Fourcade in 1986 (\uc9l\ue9gie L apostrophe E.C.) in reference to an epoch, but also to a new sense of experiencing time and space in the so-called \uab age of digital reproducibility \ubb. The aim of this paper is to consider how the change in temporal protocols due to the triumph of Big Optics (Paul Virilio) affects the sense of teleology (destiny) and the quest for experience in French contemporary poetry (in particular, in the genre of the elegy). Including both memory and anticipation, the \uab extr\ueame contemporain \ubb production seems to prefer the \u201ctime of now\u201d, Jetz-zeit in Benjamin\u2019s words, to past or testimony, and speaks to the present, whose responsibility is to give voice to a space where everything is simply allowed to happen

Analyse qualitative par Chromatographie Couche Mince Haute performance (HPTLC) des céramides et lipides neutres du stratum corneum

LYON1-BU Santé (693882101) / SudocSudocFranceF

L’habitat Bronze final-Hallstatt ancien de « la grande pièce » à Fontenay-le-Marmion (Calvados)

Ce site de la Campagne de Caen, occupé depuis le Néolithique, comprend une occupation de la fin de l’âge du Bronze et du début du Premier âge du Fer. Des vestiges de cette période, d’une grande diversité, ont été mis au jour : un fossé, des structures sur poteaux, des fosses, des fours domestiques, des fours à alandier et une carrière d’extraction. Cet habitat assez dense pourrait s’étendre sur une dizaine d’hectares. L’ensemble céramique du Bronze final/Hallstatt C est, avec celui d’Ifs « Object’Ifs Sud », le plus important de Basse-Normandie.Situated on the Caen plain, this site, first occupied during the Neolithic period, comprises an occupation dating to the Bronze Age and the early Hallstatt period. A wide range of features have been revealed: ditches, post structures, pits, domestic ovens, kilns with flues and an extraction pit. This reasonably dense settlement seems to spread over about ten hectares. The late Bronze Age/Hallstatt C pottery assemblage is, along with that from Ifs “Object’Ifs Sud”, the most consequent in Lower-Normandy

The depletion of F1 subunit {varepsilon} in yeast leads to an uncoupled respiratory phenotype that is rescued by mutations in the proton translocating subunits of F0.

International audience: The central stalk of the ATP synthase is an elongated hetero-oligomeric structure, providing a physical connection between the catalytic sites in F1 and the proton translocation channel in F0 for energy transduction between the two subdomains. The shape of the central stalk and relevance to energy coupling is essentially the same in ATP synthases from all forms of life, yet the protein composition of this domain changed during evolution of the mitochondrial enzyme from a two-subunit to three-subunit structure (γ,δ,ε). Whereas the mitochondrial γ and δ-subunits are homologues of the bacterial central stalk proteins, the deliberate addition of subunit ε remains poorly understood. Here we report that down-regulation of the gene (ATP15) encoding ε-subunit rapidly leads to lethal F0-mediated proton leaks through the membrane because of the loss of stability of the ATP synthase. The ε-subunit is thus essential for oxidative phosphorylation. Moreover, mutations in F0 subunits a and c that slow the proton translocation rate were identified that prevent epsilon-deficient ATP synthases from dissipating the electrochemical potential. Cumulatively, our data lead us to propose that the ε-subunit evolved to permit operation of the central stalk under the torque imposed at the normal speed of proton movement through mitochondrial F0

The substitution of Proline 168 favors Bax oligomerization and stimulates its interaction with LUVs and mitochondria

International audienceBax is a major player in the apoptotic process, being at the core of the mitochondria permeabilization events. In spite of the major recent advances in the knowledge of Bax organization within the membrane, the precise behavior of the C-terminal helix α9 remains elusive, since it was absent from the resolved structure of active Bax. The Proline 168 (P168) residue, located in the short loop between α8 and α9, has been the target of site-directed mutagenesis experiments, with conflicting results. We have produced and purified a recombinant mutant Bax-P168A, and we have compared its behavior with that of wild-type Bax in a series of tests on Large Unilamellar Vesicles (LUVs) and isolated mitochondria. We conclude that Bax-P168A had a greater ability to oligomerize and bind to membranes. Bax-P168A was not more efficient than wild-type Bax to permeabilize liposomes to small molecules but was more prone to release cytochrome c from mitochondria

Lethal Accumulation of Guanylic Nucleotides in Saccharomyces cerevisiae HPT1-Deregulated Mutants

Guanylic nucleotide biosynthesis is a conserved and highly regulated process. Drugs reducing GMP synthesis affect the immunological response and mutations enabling guanylic-derivative recycling lead to severe mental retardation. While the effects of decreased GMP synthesis have been well documented, the consequences of GMP overproduction in eukaryotes are poorly understood. In this work, we selected and characterized several mutations making yeast hypoxanthine–guanine phosphoribosyltransferase insensitive to feedback inhibition by GMP. In these mutants, accumulation of guanylic nucleotides can be triggered by addition of extracellular guanine. We show that such an accumulation is highly toxic for yeast cells and results in arrest of proliferation and massive cell death. This growth defect could be partially suppressed by overexpression of Rfx1p, a transcriptional repressor of the DNA damage response pathway. Importantly, neither guanylic nucleotide toxicity nor its suppression by Rfx1p was associated with an alteration of forward mutation frequency

Experimental Relocation of the Mitochondrial ATP9 Gene to the Nucleus Reveals Forces Underlying Mitochondrial Genome Evolution

Only a few genes remain in the mitochondrial genome retained by every eukaryotic organism that carry out essential functions and are implicated in severe diseases. Experimentally relocating these few genes to the nucleus therefore has both therapeutic and evolutionary implications. Numerous unproductive attempts have been made to do so, with a total of only 5 successes across all organisms. We have taken a novel approach to relocating mitochondrial genes that utilizes naturally nuclear versions from other organisms. We demonstrate this approach on subunit 9/c of ATP synthase, successfully relocating this gene for the first time in any organism by expressing the ATP9 genes from Podospora anserina in Saccharomyces cerevisiae. This study substantiates the role of protein structure in mitochondrial gene transfer: expression of chimeric constructs reveals that the P. anserina proteins can be correctly imported into mitochondria due to reduced hydrophobicity of the first transmembrane segment. Nuclear expression of ATP9, while permitting almost fully functional oxidative phosphorylation, perturbs many cellular properties, including cellular morphology, and activates the heat shock response. Altogether, our study establishes a novel strategy for allotopic expression of mitochondrial genes, demonstrates the complex adaptations required to relocate ATP9, and indicates a reason that this gene was only transferred to the nucleus during the evolution of multicellular organisms