Journal Articles
Large Exciton Energy Shifts by Reversible Surface Exchange in 2D II–VI Nanocrystals
Conjugation between σ- and π-Aromaticity in 1-C-Arylated Monocarba-closo-dodecaborate Anions
Stereospecific Rhodium-Catalyzed Allylic Substitution with Alkenyl Cyanohydrin Pronucleophiles: Construction of Acyclic Quaternary Substituted α,β-Unsaturated Ketones
Syntheses of Dimeric Tetrahydroxanthones with Varied Linkages: Investigation of “Shapeshifting” Properties
Issue Information
In This Issue
Operando Analysis of NiFe and Fe Oxyhydroxide Electrocatalysts for Water Oxidation: Detection of Fe4+ by Mössbauer Spectroscopy
Mechanistic Insights into the H2S-Mediated Reduction of Aryl Azides Commonly Used in H2S Detection
Tumor Acidity-Sensitive Polymeric Vector for Active Targeted siRNA Delivery
Correlating Microstructural Lithium Metal Growth with Electrolyte Salt Depletion in Lithium Batteries Using 7Li MRI
In Situ Observation of Active Oxygen Species in Fe-Containing Ni-Based Oxygen Evolution Catalysts: The Effect of pH on Electrochemical Activity
Reads2Type: a web application for rapid microbial taxonomy identification
Outer domains of integrase within retroviral intasomes are dispensible for catalysis of DNA integration
Retroviral DNA integration is mediated by nucleoprotein complexes (intasomes) comprising a pair of viral DNA ends synapsed by a tetramer of integrase. Current integrase inhibitors act on intasomes rather than free integrase protein. Structural and functional studies of intasomes are essential to understand their mechanism of action and how the virus can escape by mutation. To date, prototype foamy virus (PFV) is the only retrovirus for which high-resolution structures of intasomes have been determined. In the PFV intasome structure, only the core domains of the outer subunits are ordered; the N-terminal domain, C-terminal domain, and N-terminal extension domain are disordered. Are these “missing domains” required for function or are they dispensable? We have devised a strategy to assemble “hetero-intasomes” in which the outer domains are not present as a tool to assess the functional role of the missing domains for catalysis of integration. We find that the disordered domains of outer subunits are not required for intasome assembly or catalytic activity as catalytic core domains can substitute for the outer subunits in the case of both PFV and HIV-1 intasomes.
Effect of methylation on the side-chain pKa value of arginine
Arginine methylation is important in biological systems. Recent studies link the deregulation of protein arginine methyltransferases with certain cancers. To assess the impact of methylation on interaction with other biomolecules, the pKa values of methylated arginine variants were determined using NMR data. The pKa values of monomethylated, symmetrically dimethylated, and asymmetrically dimethylated arginine are similar to the unmodified arginine (14.2 ± 0.4). Although the pKa value has not been significantly affected by methylation, consequences of methylation include changes in charge distribution and steric effects, suggesting alternative mechanisms for recognition.
Structural investigations of the p53/p73 homologs from the tunicate species Ciona intestinalis reveal the sequence requirements for the formation of a tetramerization domain
Most members of the p53 family of transcription factors form tetramers. Responsible for determining the oligomeric state is a short oligomerization domain consisting of one β-strand and one α-helix. With the exception of human p53 all other family members investigated so far contain a second α-helix as part of their tetramerization domain. Here we have used nuclear magnetic resonance spectroscopy to characterize the oligomerization domains of the two p53-like proteins from the tunicate Ciona intestinalis, representing the closest living relative of vertebrates. Structure determination reveals for one of the two proteins a new type of packing of this second α-helix on the core domain that was not predicted based on the sequence, while the other protein does not form a second helix despite the presence of crucial residues that are conserved in all other family members that form a second helix. By mutational analysis, we identify a proline as well as large hydrophobic residues in the hinge region between both helices as the crucial determinant for the formation of a second helix.
Single fluorescence probes along the reactive center loop reveal site-specific changes during the latency transition of PAI-1
The serine protease inhibitor (serpin), plasminogen activator inhibitor-1 (PAI-1), is an important biomarker for cardiovascular disease and many cancers. It is therefore a desirable target for pharmaceutical intervention. However, to date, no PAI-1 inhibitor has successfully reached clinical trial, indicating the necessity to learn more about the mechanics of the serpin. Although its kinetics of inhibition have been extensively studied, less is known about the latency transition of PAI-1, in which the solvent-exposed reactive center loop (RCL) inserts into its central β-sheet, rendering the inhibitor inactive. This spontaneous transition is concomitant with a large translocation of the RCL, but no change in covalent structure. Here, we conjugated the fluorescent probe, NBD, to single positions along the RCL (P13-P5′) to detect changes in solvent exposure that occur during the latency transition. The results support a mousetrap-like RCL-insertion that occurs with a half-life of 1–2 h in accordance with previous reports. Importantly, this study exposes unique transitions during latency that occur with a half-life of ∼5 and 25 min at the P5′ and P8 RCL positions, respectively. We hypothesize that the process detected at P5′ represents s1C detachment, while that at P8 results from a steric barrier to RCL insertion. Together, these findings provide new insights by characterizing multiple steps in the latency transition.
Evidence for an essential role of intradimer interaction in catalytic function of carnosine dipeptidase II using electrospray-ionization mass spectrometry
Carnosine dipeptidase II (CN2/CNDP2) is an M20 family metallopeptidase that hydrolyses various dipeptides including β-alanyl-l-histidine (carnosine). Crystallographic analysis showed that CN2 monomer is composed of one catalytic and one dimerization domains, and likely to form homodimer. In this crystal, H228 residue of the dimerization domain interacts with the substrate analogue bestatin on the active site of the dimer counterpart, indicating that H228 is involved in enzymatic reaction. In the present study, the role of intradimer interaction of CN2 in its catalytic activity was investigated using electrospray-ionization time-of-flight mass spectrometry (ESI-TOF MS). First, a dimer interface mutant I319K was prepared and shown to be present as a folded monomer in solution as examined by using ESI-TOF MS. Since the mutant was inactive, it was suggested that dimer formation is essential to its enzymatic activity. Next, we prepared H228A and D132A mutant proteins with different N-terminal extended sequences, which enabled us to monitor dimer exchange reaction by ESI-TOF MS. The D132A mutant is a metal ligand mutant and also inactive. But the activity was partially recovered time-dependently when H228A and D132A mutant proteins were incubated together. In parallel, H228A/D132A heterodimer was formed as detected by ESI-TOF MS, indicating that interaction of a catalytic center with H228 residue of the other subunit is essential to the enzymatic reaction. These results provide evidence showing that intradimer interaction of H228 with the reaction center of the dimer counterpart is essential to the enzymatic activity of CN2.
The way forward is through Paris
The way forward is through Paris
Nature 527, 7579 (2015). doi:10.1038/527409a
Leaders must come together on a solid agreement at the United Nations climate conference — and then get to work at home by meeting commitments and finding new ways to reduce emissions.
Built on trust
Built on trust
Nature 527, 7579 (2015). doi:10.1038/527410a
Written agreements between parties in research collaborations are not a sign of a lack of faith.
A ‘perfect’ agreement in Paris is not essential
A ‘perfect’ agreement in Paris is not essential
Nature 527, 7579 (2015). http://www.nature.com/doifinder/10.1038/527411a
Author: Johan Rockström
Success at the latest climate talks will be a recognition by the world’s nations that incremental change will not do the job, says Johan Rockström.