α-carboxysomes are large, heterogeneous bodies that fix CO2 in cyanobacteria. In this issue of Structure, Evans et al. (2023) report a cryo-electron microscopy study of the α-carboxysome from Cyanobium sp. PCC 7001 along with modeling of its icosahedral shell and the packing of RuBisCO within its interior.

Amino acid deletions are high-risk, high-reward mutations, yet structural consequences are poorly understood. In this issue of Structure, Woods et al. (2023) individually deleted 65 residues from a small α-helical protein, structurally assayed the 17 soluble variants, and developed a computational model of deletion solubility combining Rosetta and AlphaFold2.

Before engaging G protein-coupled receptors (GPCRs) to transduce extracellular signals, heterotrimeric G proteins (Gαβγ) must fold properly with the help of chaperones. In this issue of Structure, Papasergi-Scott et al. (2023) unveil the molecular basis for how mammalian Ric-8 chaperones achieve selectivity for their respective Gα subunit clients.

In this issue of Structure, Huber et al. identify five O-methyltransferases, and three of them catalyze the sequential methylation of the Gram-negative bacterium-derived aromatic polyketide anthraquinone AQ-256. They present co-crystal structures with bound AQ-256 and its methylated derivatives, which explains the specificities of these O-methyltransferases.

Sunny days for chloroplast protein import: Srinivasan et al. (2023) report on the isolation and provide the first structural information on the pea TOC complex that mediates protein translocation across the outer chloroplast membrane. While two cryoEM structures for algal import complexes have been published, this is the gateway to long-sought-after structures from land plants.

In this issue of Structure, Buel et al. (2023) combined NMR data with AlphaFold2 to map out the interaction between the AZUL domain of ubiquitin ligase E6AP and UBQLN1/2 UBA. The authors demonstrated that this interaction enhances the self-association of the helix neighboring UBA and enables E6AP to localize to UBQLN2 droplets.

In this issue of Structure, Zhang et al. report their structural studies on the C2 and PH domains of Ca2+-dependent activator proteins for secretion (CAPS). The two domains form a tightly packed module and generate a continuous basic patch across both domains to substantially enhance CAPS binding to PI(4,5)P2-containing membranes.

In this issue of Structure, Wen et al. present the cryo-EM structure of the aryl hydrocarbon receptor (AhR) and show how it is recruited and stabilized by the HSP90 molecular chaperone and its co-chaperones XAP2 and p23.

In this issue of Structure, Mabanglo et al. characterize five ClpP agonists termed TRs. The co-crystal structures reveal more robust shape and charge complementarities than the anti-cancer agent ONC201. These novel compounds are of potential therapeutic interest because they enhance ClpP proteolytic activity and have an inhibitory effect on tumor cell growth.

In this issue of Structure, Wang et al. investigate the interplay between folded and disordered regions of the SARS-CoV-2 non-structural protein 1 (Nsp1) that promotes the suppression of host protein translation. Their investigation will lead to novel avenues to therapeutically target critical viral functions necessary for host immune-response suppression.

In this issue of Structure, Dazzoni et al. solve the high-resolution homo- and hetero-dimeric structures of the Klebsiella oxytoca PulL and PulM C-terminal domains and unravel an uncharacterized dynamic interaction interface that is required for correct function of the type II secretion system.