ACS DIVISION OF BIOLOGICAL CHEMISTRY

April 2nd, 2018 by Dominik A. Herbst

The structural organization of substrate loading in iterative polyketide synthases

The structural organization of substrate loading in iterative polyketide synthases, Published online: 02 April 2018; doi:10.1038/s41589-018-0026-3

The crystal structure and cryo-electron microscopy of the loading/condensing region of a nonreducing polyketide synthase reveals the insertion of a starter-unit acyltransferase into the condensing region and an asymmetrical post-loading state.

April 2nd, 2018 by Taka A. Tsunoyama

Super-long single-molecule tracking reveals dynamic-anchorage-induced integrin function

Super-long single-molecule tracking reveals dynamic-anchorage-induced integrin function, Published online: 02 April 2018; doi:10.1038/s41589-018-0032-5

Dissolved oxygen and a reducing-plus-oxidizing system suppress photobleaching and photoblinking in single-molecule tracking experiments, allowing long recordings of CD47 and integrin that showed temporary immobilization within focal adhesions.

April 2nd, 2018 by Michael M. Gaschler

FINO₂ initiates ferroptosis through GPX4 inactivation and iron oxidation

FINO₂ initiates ferroptosis through GPX4 inactivation and iron oxidation, Published online: 02 April 2018; doi:10.1038/s41589-018-0031-6

FINO2 is a small molecule that requires the endoperoxide moiety and hydroxyl group to promote ferroptosis through indirect inhibition of GPX4 enzymatic function and direct oxidation of iron, resulting in increased lipid peroxidation.

March 29th, 2018 by Hans Gaus, Colton M. Miller, Punit P. Seth, Edward N. Harris

March 27th, 2018 by Daniel N Mariappa, Andrew Ferenbach, Daan M.F. van Aalten

Post-translational modification of serine/threonine residues in nucleocytoplasmic proteins with N-acetylglucosamine (O-GlcNAcylation) is an essential regulatory mechanism in many cellular processes. In Drosophila, null mutants of the polycomb gene O-GlcNAc transferase (OGT, also known as super sex combs [sxc]) display homeotic phenotypes. To dissect the requirement for O-GlcNAc signaling in Drosophila development, we used CRISPR/Cas9 gene editing to generate rationally designed sxc catalytically hypomorphic or null point mutants. Of the fertile males derived from embryos injected with the CRISPR/Cas9 reagents, 25% produced progeny carrying precise point mutations with no detectable off-target effects. One of these mutants, the catalytically inactive sxcK872M, was recessive lethal, whereas a second mutant, the hypomorphic sxcH537A, was homozygous viable. We observed that reduced total protein O-GlcNAcylation in the sxcH537A mutant is associated with a wing vein phenotype and temperature-dependent lethality. Genetic interaction between sxcH537A and a null allele of Drosophila host cell factor (dHcf), encoding an extensively O-GlcNAcylated transcriptional coactivator, resulted in abnormal scutellar bristle numbers. A similar phenotype was also observed in sxcH537A flies lacking a copy of skuld (skd), a Mediator complex gene known to affect scutellar bristle formation. Interestingly, this phenotype was independent of OGT Polycomb function or dHcf downstream targets. In conclusion, the generation of the endogenous OGT hypomorphic mutant sxcH537A enabled us to identify pleiotropic effects of globally reduced protein O-GlcNAc during Drosophila development. The mutants generated and phenotypes observed in this study provide a platform for discovery of OGT substrates that are critical for Drosophila development.

March 27th, 2018 by Yanbo Yang, Minhyoung Lee, Gregory D. Fairn

Membrane biology seeks to understand how lipids and proteins within bilayers assemble into large structures such as organelles and the plasma membrane. Historically, lipids were thought to merely provide structural support for bilayer formation and membrane protein function. Research has now revealed that phospholipid metabolism regulates nearly all cellular processes. Sophisticated techniques helped identify >10,000 lipid species, suggesting that lipids support many biological processes. Here, we highlight the synthesis of the most abundant glycerophospholipids classes and their distribution in organelles. We review vesicular and nonvesicular transport pathways shuttling lipids between organelles and discuss lipid regulators of membrane trafficking and second messengers in eukaryotic cells.

March 27th, 2018 by Amanda J. Chase, Rebecka Wombacher, Oliver T. Fackler

The HIV-1 pathogenicity factor Nef enhances viral replication by modulating multiple host cell pathways, including tuning the activation state of infected CD4 T lymphocytes to optimize virus spread. For this, Nef inhibits anterograde transport of the Src family kinase (SFK) Lck toward the plasma membrane (PM). This leads to retargeting of the kinase to the trans-Golgi network (TGN), while the intracellular transport of a related SFK, Fyn, is unaffected by Nef. The 18 amino acid SH4 domain membrane anchor of Lck is necessary and sufficient for Nef-mediated retargeting, but other details of this process are not known. The goal of this study was therefore to identify characteristics of SH4 domains responsive to Nef and the transport machinery used. Screening a panel of SFK SH4 domains revealed two groups that were sensitive or insensitive for TGN retargeting by Nef, as well as the importance of the amino acid at position 8 for determining Nef-sensitivity. Anterograde transport of Nef-sensitive domains was characterized by slower delivery to the PM and initial targeting to Golgi membranes, where transport was arrested in the presence of Nef. For Nef-sensitive SH4 domains, ectopic expression of the lipoprotein binding chaperone (LPC) Unc119a or the GTPase Arl3 or reduction of their endogenous expression phenocopied the effect of Nef. Together, these results suggest that (i) analogous to K-Ras, Nef-sensitive SH4 domains are transported to the PM by a cycle of solubilization and membrane insertion and (ii) intrinsic properties define SH4 domains as cargo of this Nef-sensitive LPC-GTPase transport cycle.

March 26th, 2018 by Aisha Yesbolatova

TAGing for destruction

TAGing for destruction, Published online: 26 March 2018; doi:10.1038/s41589-018-0024-5

Proteins brought to an E3 ubiquitin ligase are polyubiquitylated for rapid degradation via the proteasome. A new study developed a tag-based degradation system using heterobifunctional degradation inducers called dTAGs, which rapidly depleted FKBP12F36V-fused proteins in cultured cells and in mice.

March 26th, 2018 by Behnam Nabet

The dTAG system for immediate and target-specific protein degradation

The dTAG system for immediate and target-specific protein degradation, Published online: 26 March 2018; doi:10.1038/s41589-018-0021-8

The dTAG system pairs potent heterobifunctional degraders and extensible tagging strategies to achieve immediate and reversible degradation of divergent proteins, facilitating biological investigation and drug target validation in cells and in mice.

March 26th, 2018 by Jakub Rajniak

Biosynthesis of redox-active metabolites in response to iron deficiency in plants

Biosynthesis of redox-active metabolites in response to iron deficiency in plants, Published online: 26 March 2018; doi:10.1038/s41589-018-0019-2

The biosynthesis and secretion of redox-active coumarins sideretin and fraxetin in Arabidopsis thaliana enables the plant to acquire iron under nutrient-limited conditions and provides a blueprint for the use of related compounds in other eudicots.