Activation of plant immunity through conversion of a helper NLR homodimer into a resistosome.

Nucleotide-binding domain and leucine-rich repeat (NLR) proteins can engage in complex interactions to detect pathogens and execute a robust immune response via downstream helper NLRs. However, the biochemical mechanisms of helper NLR activation by upstream sensor NLRs remain poorly understood. Here, we show that the coiled-coil helper NLR NRC2 from Nicotiana benthamiana accumulates in vivo as a homodimer that converts into a higher-order oligomer upon activation by its upstream virus disease resistance protein Rx.

Resurrection of plant disease resistance proteins via helper NLR bioengineering.

Parasites counteract host immunity by suppressing helper nucleotide binding and leucine-rich repeat (NLR) proteins that function as central nodes in immune receptor networks. Understanding the mechanisms of immunosuppression can lead to strategies for bioengineering disease resistance. Here, we show that a cyst nematode virulence effector binds and inhibits oligomerization of the helper NLR protein NRC2 by physically preventing intramolecular rearrangements required for activation.

Cryo-EM structure of ssDNA bacteriophage ΦCjT23 provides insight into early virus evolution.

The origin of viruses remains an open question. While lack of detectable sequence similarity hampers the analysis of distantly related viruses, structural biology investigations of conserved capsid protein structures facilitate the study of distant evolutionary relationships. Here we characterize the lipid-containing ssDNA temperate bacteriophage ΦCjT23, which infects Flavobacterium sp.

Structural basis of rapid actin dynamics in the evolutionarily divergent Leishmania parasite.

Actin polymerization generates forces for cellular processes throughout the eukaryotic kingdom, but our understanding of the 'ancient' actin turnover machineries is limited. We show that, despite > 1 billion years of evolution, pathogenic Leishmania major parasite and mammalian actins share the same overall fold and co-polymerize with each other. Interestingly, Leishmania harbors a simple actin-regulatory machinery that lacks cofilin 'cofactors', which accelerate filament disassembly in higher eukaryotes.

Cryo-electron microscopy reveals two distinct type IV pili assembled by the same bacterium.

Type IV pili are flexible filaments on the surface of bacteria, consisting of a helical assembly of pilin proteins. They are involved in bacterial motility (twitching), surface adhesion, biofilm formation and DNA uptake (natural transformation). Here, we use cryo-electron microscopy and mass spectrometry to show that the bacterium Thermus thermophilus produces two forms of type IV pilus ('wide' and 'narrow'), differing in structure and protein composition.

The Structure of the Human Respiratory Syncytial Virus M2-1 Protein Bound to the Interaction Domain of the Phosphoprotein P Defines the Orientation of the Complex.

Human respiratory syncytial virus (HRSV) is a negative-stranded RNA virus that causes a globally prevalent respiratory infection, which can cause life-threatening illness, particularly in the young, elderly, and immunocompromised. HRSV multiplication depends on replication and transcription of the HRSV genes by the virus-encoded RNA-dependent RNA polymerase (RdRp). For replication, this complex comprises the phosphoprotein (P) and the large protein (L), whereas for transcription, the M2-1 protein is also required.

Structure and Function of the Human Respiratory Syncytial Virus M2-1 Protein.

Human respiratory syncytial virus (HRSV) is a non-segmented negative stranded RNA virus and is recognized as the most important viral agent of lower respiratory tract infection worldwide, responsible for up to 199,000 deaths each year. The only FDA-approved regime to prevent HRSV-mediated disease is pre-exposure administration of a humanized HRSV-specific monoclonal antibody, which although being effective, is not in widespread usage due to its cost. No HRSV vaccine exists and so there remains a strong need for alternative and complementary anti-HRSV therapies.