Structural basis of NPR1 in activating plant immunity We report cryo-electron microscopy and crystal structures of Arabidopsis NPR1 and its complex with the transcription factor TGA3. Cryo-electron microscopy analysis reveals that NPR1 is a bird-shaped homodimer comprising a central Broad-complex, Tramtrack and Bric-à-brac (BTB) domain, a BTB and carboxyterminal Kelch helix bundle, four ankyrin repeats and a disordered salicylic-acid-binding…
Fab-dimerized glycan-reactive antibodies are a structural category of natural antibodies Natural antibodies (Abs) can target host glycans on the surface of pathogens. We studied the evolution of glycan-reactive B cells of rhesus macaques and humans using glycosylated HIV-1 envelope (Env) as a model antigen. We describe HIV-1 Env Fab-dimerized glycan (FDG)-reactive neutralizing Abs in HIV-1 vaccinated and simian-HIV (SHIV)-infected…
Structural Basis for Virulence Activation of Francisella tularensis The bacterium Francisella tularensis (Ft) is one of the most infectious agents known. Ft virulence is controlled by a unique combination of transcription regulators: the MglA-SspA heterodimer, PigR, and the stress signal, ppGpp. MglA-SspA assembles with the σ70-associated RNAP holoenzyme (RNAPσ70), forming a virulence-specialized polymerase. These factors activate Francisella pathogenicity island…
Data-driven determination of number of discrete conformations in single-particle cryo-EM Single-particle cryo-EM can be used to image heterogeneous samples containing multiple molecular species, different oligomeric states or distinct conformations. This, however, requires expert-user knowledge and trial-and-error experimentation to determine the correct number of conformations present in a mixture. Here, we propose an approach to address the problem of automatically…
Redox-sensitive E2 Rad6 controls cellular response to oxidative stress via K63-linked ubiquitination of ribosomes In this study, we set out to investigate the key role of Rad6 in regulating cellular response to stress in budding yeast as part of the RTU. Rad6 is small (20 kDa), highly conserved, and a multifunctional E2 involved in DNA repair and in the…
Disruption of the HIV-1 Envelope allosteric network blocks CD4-induced rearrangements The trimeric HIV-1 Envelope protein (Env) mediates viral-host cell fusion via a network of conformational transitions, with allosteric elements in each protomer orchestrating host receptor-induced exposure of the co-receptor binding site and fusion elements. To understand the molecular details of this allostery, here, we introduce Env mutations aimed to…
Accurate Detection of Proteins in Cryo-Electron Tomograms from Sparse Labels Cryo-electron tomography (CET) combined with sub-volume averaging (SVA), is currently the only imaging technique capable of determining the structure of proteins imaged inside cells at molecular resolution. To obtain high-resolution reconstructions, sub-volumes containing randomly distributed copies of the protein of interest need be identified, extracted and subjected to SVA,…
Structure and dynamics of the Arabidopsis O-fucosyltransferase SPINDLY SPINDLY (SPY) in Arabidopsis thaliana is a novel nucleocytoplasmic protein O-fucosyltransferase (POFUT), which regulates diverse developmental processes. Sequence analysis indicates that SPY is distinct from ER-localized POFUTs and contains N-terminal tetratricopeptide repeats (TPRs) and a C-terminal catalytic domain resembling the O-linked-N-acetylglucosamine (GlcNAc) transferases (OGTs). However, the structural feature that determines the…
