Letters in 2008

This study presents the crystal structure of a Fas-FADD complex, a central feature of the so-called death inducing signalling complex. The structure reveals a new mode of death domain interactions that allows four FADD and four Fas proteins in one complex.

This paper shows that Desulfitobacterium hafniense pyrrolysyl-tRNA synthetase–tRNA^Pyl is an orthogonal pair in vivo and in vitro. The structure of the co-complex reveals the distinct interactions of the protein and tRNA that distinguish this pair from those which function with the twenty standard amino acids.

The CBM complex has a key role in transducing signals from the antigen receptors in T and B cells to the transcription factor NF-κB during lymphocyte activation. Casein kinase 1α (CK1α) is shown to regulate the CBM complex in two opposing ways, first promoting and then subsequently terminating receptor-induced NF-κB activity and lymphocyte activation.

Here, subdiffraction-resolution STED fluorescence microscopy is used to detect the diffusion of single lipids or GPI-anchored proteins on the plasma membrane of a living cell. Tuning the probing spot area ∼70-fold below that of a confocal microscope reveals that unlike phosphoglycerolipids, sphingolipids and GPI-anchored proteins are trapped for ∼10 ms in cholesterol-mediated complexes within <20 nm space.

In vertebrates and other deuterostomes, the molecular pathway that leads to asymmetry utilizes the signalling molecule Nodal, a member of the TGF-β superfamily. But no orthologues of Nodal have been found in the other two great groups of bilaterians. This paper finds orthologues of nodal and one of its targets, Pitx, in two species of snail, and show that loss of nodal disrupts shell coiling.

Nuclear pore complexes (NPCs) serve as gateways between the nucleus and cytoplasm and allow only the transport of selected macromolecules across the nuclear envelope. NPCs are comprised of a scaffold that anchors proteins called FG-nucleoporins, which contain disordered regions that line the inner surface of the pore and extend into the lumen. This study reports the design of an artificial membrane that functions as a selective filter in allowing efficient passage of transport factors and transport factor carrying cargo that specifically bind to FG-nucleoporins.

The chlorophyll biosynthetic enzyme NADPH:protochlorophyllide oxidoreductase, which catalyses a light-driven reaction involving hydride and proton transfers is examined. It is determined that prior excitation of the enzyme–substrate complex with a laser pulse induces a more favourable conformation of the active site and increases the catalytic efficiency of the coupled hydride and proton transfer reactions. Spectral changes in the mid-infrared after the absorption of one photon reveal significant conformational changes in the enzyme.

This study presents a global analysis of seafloor roughness derived from marine gravity data and finds that residual roughness anomalies remain over large swaths of ocean floor. The Atlantic ocean floor that formed over mantle previously overlain by the Pangaea supercontinent displays anomalously low roughness, and attribute this observation to a sub-Pangaean supercontinental mantle temperature anomaly leading to slightly thicker than normal Atlantic crust. In contrast, ocean crust formed above Pacific superswells is not associated with basement roughness anomalies.

This paper reports the discovery of a water maser at redshift 2.64 in the dust- and gas-rich gravitationally lensed type-1 quasar MG J0414+0534. Using the locally determined luminosity function, the probability of finding a maser this luminous associated with any single active galaxy is 10⁻⁶, leading to the conclusion that the volume densities and luminosities of masers are higher at that epoch.

A new family of superconductors containing layers of iron arsenide has attracted considerable interest because of their high transition temperatures and similarities with the high-T_c copper oxide superconductors. This paper reports inelastic neutron scattering observations of a magnetic resonance below T_c in Ba_0.6K_0.4Fe₂As₂, demonstrating that the superconducting energy gap has unconventional symmetry.

During clathrin-mediated endocytosis, cargo proteins are recognized by clathrin adaptors. The clathrin adaptor AP2 recognizes two major classes of endocytic motifs, including an acidic dileucine motif. This study presents the crystal structure of AP2 in complex with the diceucine motif of a cargo protein, thereby revealing the mechanism of cargo–adaptor recognition.

Substance P is a neuropeptide that evokes slow excitation after activation of its cognate G-protein-coupled receptor. This study investigates the downstream pathway and shows that it depends on Src family kinases, rather than G-protein signalling.

It is shown that the cell surface protein prominin 1 (also known as CD133) marks stem cells in the mouse intestine. Using lineage-tracing experiments, it is shown that intestinal tumours can originate in these cells when the Wnt signalling pathway is aberrantly activated.

Intestinal tumours can originate from Lgr5⁺ intestinal stem cells after genetic activation of the Wnt signalling pathway.

This study tests the importance of the intrinsic DNA sequence preferences of nucleosomes by measuring the genome-wide occupancy of nucleosomes assembled on purified yeast genomic DNA. The resulting map is similar to in vivo nucleosome maps, indicating that the organization of nucleosomes in vivo is largely governed by the underlying genomic DNA sequence.

It is shown that type of repair pathway, known as postreplication repair, permits cells to replicate their DNA when it is damaged, thereby avoiding the activation of a cellular response that would inhibit proliferation.

In sleeping adult zebra finches, forebrain premotor neuron activity is proposed to reflect daytime singing episodes. This study shows that in juvenile songbirds yet to master their song, auditory exposure to an adult 'tutor' song produced profound changes in the premotor neuronal activity during the subsequent sleep session. These changes in night time activity preceded and reflected tutor-song induced changes in singing the next day.

It is shown that after activation, Ire1 molecules cluster into discrete foci containing high order oligomers on the endoplasmic reticulum membrane. HAC1 mRNA is recruited to these foci by means of a sequence in its 3′ UTR and is processes at these sites. Disruption of either Ire1 clustering or HAC1 mRNA recruitment impairs UPR signalling. Hence HAC1 mRNA is delivered to a site where it is processed thus ensuring that it is only translated when UPR is on.

Dietary restriction can extend lifespan in various species. In mammals, intermittent fasting can also extend lifespan and reduce the incidence of age-related disorders. It is shown that intermittent fasting can effectively extend the lifespan of Caenorhabditis elegans, and that the low molecular weight GTPase RHEB-1 has a central role in lifespan regulation.

Indications of the presence of water in the atmosphere of the planet HD 189733b have recently been found in transmission spectra. This paper reports the detection of strong water absorption in a high signal-to-noise, mid-infrared emission spectrum of the planet itself. The differences between these and previous observations are significant and admit the possibility that predicted planetary-scale dynamical weather structures might alter the emission spectrum over time.