Volume 26 Issue 12, December 2019

Finally, the architecture of the translocase of the mitochondrial outer membrane (TOM complex) is revealed, after 20 years of anticipation. Two groups have now determined the near-atomic structures of the TOM complex. These findings improve understanding of the mechanisms by which TOM facilitates the passage of about 1,000 different proteins from the cytosol into the mitochondria.

Chromatin is compartmentalized spatially and temporally at multiple levels, but the precise organization of chromatin and mechanisms underlying its restructuring remain unclear. Two studies published in Cell and Nature now demonstrate the ability of chromatin to undergo liquid–liquid phase separation under physiological conditions and show that this intrinsic physicochemical property of chromatin can be regulated.

Stabilization of the 3D genome architecture surrounding DNA lesions is critical for the maintenance of genome integrity. A new report by Ochs et al. shows how 53BP1 and RIF1 assemble a higher-order structure in the vicinity of damaged chromatin to protect it from unscheduled DNA-end resection.

The structure of human SMG1–SMG8–SMG9, a PI(3)K-related protein kinase complex central to mRNA surveillance, uncovers an InsP₆-binding site in the SMG1 kinase that is conserved in mTOR and important for kinase activity.

Cocrystal and cryo-EM structures of Geobacillus kaustophilus glyQ and Bacillus subtilis glyQS T-box-tRNA complexes establish a universal mechanism of amino acid sensing on tRNAs and gene regulation by T-box riboswitches.

The crystal structure of the full-length ileS T-box–tRNA complex from Mycobacterium tuberculosis provides a complete high-resolution explanation of tRNA decoding and aminoacylation sensing by this riboregulator.

The cocrystal structure of the Nocardia farcinica ileS T-box in complex with its cognate tRNA illustrates how mRNA junctions can create specific binding sites for interacting RNAs.

The cryo-EM structure of a megacomplex between chimeric GPCR, G protein and β-arrestin in their canonical active conformations provides insight into the basis of sustained G protein signaling upon megacomplex internalization.

Biochemical and structural analysis demonstrate that simultaneous detection of poly-lysine in the exit tunnel and poly(A) in the decoding center allows ribosomes to detect aberrant mRNAs, stall elongation and trigger downstream quality control pathways.

Oligomers of human αA-crystallin are characterized structurally via a hybrid approach, combining cryo-EM, cross-linking/mass spectrometry, NMR and modeling, providing insight into their dynamic behavior and heterogeneity and revealing that oxidized oligomers can also act as chaperones.

Cryo-EM structures of MERS-CoV S glycoprotein trimer in complex with different sialosides reveal how the virus engages with sialylated receptors, providing insight into receptor specificity and selectivity.

High-resolution cryo-EM structures of the core TOM complex from Saccharomyces cerevisiae, as dimeric and tetrameric assemblies, provide new insights into the mechanism of protein translocation into mitochondria.

Cryo-EM resolution of HIV-1 Env trimer bound to CD4 and a tyrosine-sulfated, coreceptor-mimicking antibody reveals two configurations of gp120–gp41 protomers that create asymmetric Env trimer conformations on the path to membrane fusion.

Cryo-EM structure of the C-terminal domain of human APOBEC3F in complex with HIV-1 Vif and CFBβ, along with functional analyses, reveals how Vif targets a host restriction protein.