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Bacteria have toxin-antitoxin systems that can trigger cell death upon different conditions, including phage infection. The recently identified type III TA system consists of an RNA endonuclease toxin and an RNA antitoxin, and the crystal structure of the complex is now presented.
Assembly of transcriptional repression complexes involves the recruitment of different proteins to SMRT or its homolog NCoR. Now structural and functional work reveal the tetrameric organization of the oligomerization domain of TBL1 and map its interactions with SMRT and GPS2. The authors propose a model for the architecture and assembly of the corepressor complex.
The enzyme autotaxin (ATX) produces the lipid mediator LPA to stimulate cell migration and proliferation. The crystal structures of rat ATX, in its apo and inhibitor-bound forms, along with functional work, offer insight into substrate specificity and show that ATX interacts with integrins through one of its SMB domains.
Alternative splicing plays a major role in the generation of functional diversity but the underlying mechanisms remain poorly understood. In a comparative genome analysis of 73 arthropod species, spanning around 420 million years of evolution, Yongfeng and coworkers find built-in intronic elements that lead to mutual exclusive splicing. These elements are species- or clade-specific, but evolutionarily conserved at the secondary structure level.
Binding of measles virus hemagglutinin (MVH) to its cellular receptors triggers the activation of the fusion protein. The conformational changes of MVH upon receptor binding are now examined by locking the dimers using disulfide bonds, or by pulling on appropriately positioned hexahistidine tags. The results indicate that the dimer interface is pulled apart after receptor binding by twisting of the MVH heads.
The measles virus hemagglutinin (MVH) promotes viral attachment to host cells via interaction with signaling lymphocyte activation molecule (SLAM). Now the crystal structure of MVH head domain in complex with the distal domain of SLAM, together with functional work, reveals the details of this interaction and explains the effectiveness of the currently used vaccine.
In Drosophila, upregulation of genes on the single male X chromosome to match that from the two female Xs depends upon the MSL complex. The structures of complexes of MSL subunits now give insight into how the MOF histone acetyltransferase and MSL3 interact with MSL1, indicating that the latter acts as a scaffold to bring the complex together.
Understanding the structural dynamics of ribosomal components is key to understanding translation. The Z-DNA– and Z-RNA–binding domain from the human RNA editing enzyme ADAR1-L is now shown to bind to specific regions of ribosomal RNAs affecting translation, suggesting that these regions might at least transiently form Z-RNA structure not observed in crystal structures.
BiP is an Hsp70 chaperone in the endoplasmic reticulum (ER) and is crucial for protein folding and quality control. Using single-molecule and ensemble FRET, the conformational cycle of BiP has now been defined. Movement of the lid domain of BiP allows this chaperone to discriminate between peptide and protein substrates.
Telomere protein RAP1 is found in organisms from yeast to mammals, but has different functions. Now the crystal structures of the RAP1 C-terminus (RCT) with its different interacting partners, together with functional analyses, reveal a conserved interaction module used by mammalian and fission yeast Rap1 to interact with TRF2 and Taz1, respectively, to mediate telomere protection. In contrast, in budding yeast this module recruits Sir3 to telomeres to mediate transcriptional silencing.
The health of the proteome in the face of multiple and diverse challenges directly influences the health of the cell and the lifespan of the organism. A recent meeting held in Nara, Japan, provided an exciting platform for scientific exchange and provocative discussions on the biology of proteins and protein homeostasis across multiple scales of analysis and model systems.
The interaction of solvent with protein has been a major unresolved and significant problem for decades. Now, NMR techniques characterize the hydration sites of ubiquitin encapsulated within reverse micelles. This approach reveals a clustering of water molecules with similar residence times, an observation that is generally not accessible by crystallographic analyses.
