Localisation of methionine residues in bacteriorhodopsin by carbonyl 13C-NMR with sequence-specific assignments

AbstractHigh-resolution 13C-NMR experiments have been performed on bacteriorhodopsin biosynthetically labeled with carbonyl-13C amino acids and solubilized in the detergent dodecylmaltoside. 13C-NMR spectra showing good resolution were obtained in the case of labeled amino acids moderately represented in the BR sequence. For BR labeled with [13C]carbonyl methionine, several sequence-specific assignment could be performed by co-labeling with 15N amino acids or proteolysis. These assignments were used to obtain structural data on BR. Water-exposure of methionine side chains in the protein was assessed by studying, using NMR, their oxidation by hydrogen peroxide. Local secondary structure at the level of methionine residues was monitored through the effect of 1H-2H exchange on NMR spectra. It was concluded that Met32, Met68 and Met163 are peripheral while all 6 other methionine residues are deeply embedded within hydrophobic α-helices. These results confirm the current model of the BR folding and secondary structure

Interplay of packing and flip-flop in local bilayer deformation. How phosphatidylglycerol could rescue mitochondrial function in a cardiolipin-deficient yeast mutant

In a previous work, we have shown that a spatially localized transmembrane pH gradient, produced by acid micro-injection near the external side of cardiolipin-containing giant unilamellar vesicles, leads to the formation of tubules that retract after the dissipation of this gradient. These tubules have morphologies similar to mitochondrial cristae. The tubulation effect is due to direct phospholipid packing modification in the outer leaflet that is promoted by protonation of cardiolipin headgroups. Here we compare the case of cardiolipin-containing giant unilamellar vesicles with that of phosphatidylglycerol-containing giant unilamellar vesicles. Local acidification also promotes formation of tubules in the latter. However, compared to cardiolipin-containing giant unilamellar vesicles the tubules are longer, exhibit a visible pearling and have a much longer lifetime after acid micro-injection is stopped. We attribute these differences to an additional mechanism that increases monolayer surface imbalance, namely inward PG flip-flop promoted by the local transmembrane pH-gradient. Simulations using a fully non-linear membrane model as well as geometrical calculations are in agreement with this hypothesis. Interestingly, among yeast mutants deficient in cardiolipin biosynthesis, only the crd1-null mutant, which accumulates phosphatidylglycerol, displays significant mitochondrial activity. Our work provides a possible explanation of such a property and further emphasizes the salient role of specific lipids in mitochondrial function.Comment: 28 pages, 10 figure

The Innovative Medicines Initiative: an engine for regulatory science.

Since its launch in 2008, the Innovative Medicines Initiative has catalysed the formation of many consortia to address challenges in drug development and regulation. As it moves into its second phase, we highlight key outcomes so far and the lessons learned.info:eu-repo/semantics/publishe

Habiter les berges. Réflexion sur les outils du projet à grande échelle

ENSA Paris-Val de Seine, DAPA & DGHU

Changer de posture face au « grand territoire »

Supplément au numéro 15

Réflexion sur les outils du projet à grande échelle "habiter les berges": Rapport de Recherche pour le Bureau de la <br />Recherche Architecturale, Urbaine et Paysagère et le Plan Urbanisme Construction Architecture (PUCA)

94 p

Réflexion sur les outils du projet à grande échelle "habiter les berges": Rapport de Recherche pour le Bureau de la <br />Recherche Architecturale, Urbaine et Paysagère et le Plan Urbanisme Construction Architecture (PUCA)

94 p