A β Strand Lock Exchange for Signal Transduction in TonB-Dependent Transducers on the Basis of a Common Structural Motif

SummaryTransport of molecules larger than 600 Da across the outer membrane involves TonB-dependent receptors and TonB-ExbB-ExbD of the inner membrane. The transport is energy consuming, and involves direct interactions between a short N-terminal sequence of receptor, called the TonB box, and TonB. We solved the structure of the ferric pyoverdine (Pvd-Fe) outer membrane receptor FpvA from Pseudomonas aeruginosa in its apo form. Structure analyses show that residues of the TonB box are in a β strand which interacts through a mixed four-stranded β sheet with the periplasmic signaling domain involved in interactions with an inner membrane sigma regulator. In this conformation, the TonB box cannot form a four-stranded β sheet with TonB. The FhuA-TonB or BtuB-TonB structures show that the TonB-FpvA interactions require a conformational change which involves a β strand lock-exchange mechanism. This mechanism is compatible with movements of the periplasmic domain deduced from crystallographic analyses of FpvA, FpvA-Pvd, and FpvA-Pvd-Fe

Recruitment of cellular prion protein to mitochondrial raft-like microdomains contributes to apoptosis execution

PrPC is identified as a new component of mitochondrial raft-like microdomains in T cells undergoing CD95/Fas–mediated apoptosis, and microtubular network integrity and function could play a role in the redistribution of PrPC from the plasma membrane to the mitochondria

Groundwater in catchments headed by temperate glaciers: A review

International audienceCatchments headed by temperate glaciers are severely impacted by climate change, and extensively studied from glaciological and surface hydrology perspectives. However groundwater in the same catchments is much more seldom mentioned, and even less studied. The few available studies found in the scientific literature tend to show a particularly high recharge of aquifers by glacial meltwater, a strong connection between surface and ground waters, and quite high hydraulic permeability in moraines and tills aquifers. New and more systematic studies could confirm and details these results. Such characteristics suggest that groundwater in coastal catchments headed by temperate glaciers could feed offshore fresh groundwater stocks. The role of potential deeper aquifers in fractured bedrock remains completely unknown.The numerous examples of natural hazards and of the sensitivity of water resources to the water cycle in catchments headed by temperate glaciers underline the importance of the study of hydrogeology, and of socioeconomic aspects, in these catchments where population is glacier-dependant. The study of groundwater in catchments headed by temperate glaciers is just at the start and there is much tobe studied