Abstract Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the pathogen that causes disease COVID-19, produces replicase polyproteins 1a and 1ab contain, respectively, 11 or 16 nonstructural proteins (nsp). Nsp5 is main protease (M pro ) responsible for cleavage at eleven positions along these polyproteins, including its own N- C-terminal boundaries, representing essential processing events subsequent viral assembly maturation. We have determined X-ray crystallographic structures...

The bacterial type III secretion system, or injectisome, is a syringe shaped nanomachine essential for the virulence of many disease causing Gram-negative bacteria. At core injectisome structure needle complex, continuous channel formed by highly oligomerized inner and outer membrane hollow rings polymerized helical filament which spans through projects into infected host cell. Here we present near-atomic resolution complex from prototypical Salmonella Typhimurium SPI-1 with local masking...

Abstract The IL-17 family of cytokines and receptors have central roles in host defence against infection development inflammatory diseases 1 . compositions structures functional ligand–receptor signalling assemblies remain unclear. IL-17E (also known as IL-25) is a key regulator type 2 immune responses driver diseases, such allergic asthma, requires both receptor A (IL-17RA) IL-17RB to elicit Here we studied IL-25–IL-17RB binary IL-25–IL-17RB–IL-17RA ternary complexes using combination...

Abstract Leptin is an adipocyte-derived protein hormone that promotes satiety and energy homeostasis by activating the leptin receptor (LepR)–STAT3 signaling axis in a subset of hypothalamic neurons. dysregulated obesity, however, where appetite remains elevated despite high levels circulating leptin. To gain insight into mechanism activation, here we determine structure stabilized leptin-bound LepR complex using single particle cryo-EM. The reveals asymmetric architecture which induces...

Janus kinases (JAKs) mediate signal transduction downstream of cytokine receptors. Cytokine-dependent dimerization is conveyed across the cell membrane to drive JAK dimerization, trans-phosphorylation, and activation. Activated JAKs in turn phosphorylate receptor intracellular domains (ICDs), resulting recruitment, phosphorylation, activation transducer activator transcription (STAT)-family factors. The structural arrangement a JAK1 dimer complex with IFNλR1 ICD was recently elucidated while...

Wnt morphogens are critical for embryonic development and tissue regeneration. Canonical Wnts form ternary receptor complexes composed of tissue-specific Frizzled (Fzd) receptors together with the shared LRP5/6 coreceptors to initiate β-catenin signaling. The cryo-EM structure a initiation complex an affinity-matured XWnt8–Frizzled8–LRP6 elucidates basis coreceptor discrimination by canonical means their N termini linker domains that engage LRP6 E1E2 domain funnels. Chimeric bearing modular...

Interleukin 27 (IL-27) is a heterodimeric cytokine that functions to constrain T cell-mediated inflammation and plays an important role in immune homeostasis. Binding of IL-27 cell surface receptors, IL-27Rα gp130, results activation receptor-associated Janus Kinases nuclear translocation Signal Transducer Activator Transcription 1 (STAT1) STAT3 transcription factors. Despite the emerging therapeutic importance this axis cancer autoimmunity, molecular blueprint receptor signaling complex,...

Thrombopoietin (THPO or TPO) is an essential cytokine for hematopoietic stem cell (HSC) maintenance and megakaryocyte differentiation. Here, we report the 3.4 Å resolution cryoelectron microscopy structure of extracellular TPO-TPO receptor (TpoR MPL) signaling complex, revealing basis homodimeric MPL activation providing a structural rationalization genetic loss-of-function thrombocytopenia mutations. The guided engineering TPO variants (TPOmod) with spectrum activities, from neutral...

Cytokines regulate immune responses by binding to cell surface receptors, including the common subunit beta (βc), which mediates signaling for GM-CSF, IL-3, and IL-5. Despite known roles in inflammation, structural basis of IL-5 receptor activation remains unclear. We present cryo-EM structure human ternary complex, revealing architectural principles IL-5, IL-3. In mammalian culture, single-molecule imaging confirms hexameric complex formation on surfaces. Engineered chimeric receptors show...

The loading of processed peptides on to major histocompatibility complex II (MHC-II) molecules for recognition by T cells is vital cell-mediated adaptive immunity. As part this process, MHC-II associates with the invariant chain (Ii) during biosynthesis in endoplasmic reticulum prevent premature peptide and serve as a scaffold subsequent proteolytic processing into MHC-II-CLIP. Cryo–electron microscopy structures full-length Human Leukocyte Antigen-DR (HLA-DR) HLA-DQ complexes associated Ii,...

Abstract The bacterial cell wall plays a crucial role in viability and is an important drug target. In Escherichia coli , the peptidoglycan crosslinking reaction to form primarily carried out by penicillin-binding proteins that catalyse D,D-transpeptidase activity. However, alternate mechanism involving L,D-transpeptidase YcbB can lead bypass of D,D-transpeptidation beta-lactam resistance. Here, we show crystallographic structure consists conserved catalytic domain decorated with subdomain...

Abstract Wall teichoic acid (WTA) is a polyol phosphate polymer that covalently decorates peptidoglycan of gram-positive bacteria, including Staphylococcus aureus . Central to WTA biosynthesis flipping lipid-linked precursors across the cell membrane by TarGH, type V ABC transporter. Here, we present cryo-EM structures S. TarGH in presence targocil-II, promising small-molecule lead with β-lactam antibiotic synergistic action. Targocil-II binds extracellular dimerisation interface TarG,...

Interleukin-21 (IL-21) plays a critical role in generating immunological memory by promoting the germinal center reaction, yet clinical use of IL-21 remains challenging because its pleiotropy and association with autoimmune disease. To better understand structural basis signaling, we determine structure IL-21–IL-21R–γc ternary signaling complex X-ray crystallography dimer trimeric complexes using cryo-electron microscopy. Guided structure, design analogs introducing substitutions to IL-21–γc...

Escherichia coli has four SPOR proteins that bind peptidoglycan, of which FtsN is essential for cell division. DamX and DedD are suggested to have semiredundant functions in division based on genetic evidence. Here, we solved the structure domain DedD, show both interact with stimulate synthetic activity peptidoglycan synthases PBP1A PBP1B, suggesting these class A PBP enzymes act concert peptidoglycan-binding during

The pathway for the biosynthesis of bacterial cell wall is one most prolific antibiotic targets, exemplified by widespread use β-lactam antibiotics. Despite this, our structural understanding class A penicillin binding proteins, which perform last two steps in this pathway, incomplete due to inherent difficulty their crystallization and complexity substrates. Here, we determine near atomic resolution structure 83 kDa PBP from Escherichia coli, PBP1b, using cryogenic electron microscopy a...

Staphylococcus aureus, an ESKAPE pathogen, is a major clinical concern due to its pathogenicity and manifold antimicrobial resistance mechanisms. The commonly used β-lactam antibiotics target bacterial penicillin-binding proteins (PBPs) inhibit crosslinking of peptidoglycan strands that comprise the cell wall mesh, initiating cascade effects leading death. S. aureus PBP1 involved in synthesis during division presence essential for survival both antibiotic susceptible resistant strains. Here,...

Membrane receptor guanylyl cyclases play a role in many important facets of human physiology, from regulating blood pressure to intestinal fluid secretion. The structural mechanisms which influence these physiological processes have yet be explored. We present the 3.9 Å resolution cryo-EM structure membrane cyclase GC-C complex with Hsp90 and its co-chaperone Cdc37, providing insight into mechanism Cdc37 mediated binding regulatory complex. As protein non-kinase client Hsp90–Cdc37, this work...

Membrane receptor guanylyl cyclases play a role in many important facets of human physiology, from regulating blood pressure to intestinal fluid secretion. The structural mechanisms which influence these physiological processes have yet be explored. We present the 3.9 Å resolution cryo-EM structure membrane cyclase GC-C complex with Hsp90 and its co-chaperone Cdc37, providing insight into mechanism Cdc37 mediated binding regulatory complex. As protein non-kinase client Hsp90–Cdc37, this work...

Peptidoglycan (PG) is an essential component of the bacterial cell wall and assembled from a lipid II precursor by glycosyltransferase transpeptidase reactions catalyzed in particular bifunctional class A penicillin-binding proteins (aPBPs). In major clinical pathogen Pseudomonas aeruginosa, PBP1B anchored within cytoplasmic membrane but regulated bespoke outer membrane-localized lipoprotein known as LpoP. Here, we report structure LpoP, showing extended N-terminal, flexible tether followed...

The bacterial cell wall plays a key role in viability and is an important drug target. made of elongated polymers that are cross-linked to one another form load-bearing mesh. An alternative cross-linking mechanism used by the l , d -transpeptidase YcbB has been implicated stress-regulated roles β-lactam resistance, outer membrane defect rescue, typhoid toxin release. for this stress-linked context host infection was unclear.

CD45 is a cell surface phosphatase that shapes the T receptor signaling threshold but does not have known ligand. A family of adenovirus proteins, including E3/49K, exploits to evade immunity by binding extracellular domain CD45, resulting in suppression signaling. We determined cryo-EM structure this complex and found E3/49K protein composed three immunoglobulin domains assembled as "beads on string" compel into closely abutted dimer cross-linking D3 domain, leading steric inhibition its...

Abstract Membrane receptor guanylyl cyclases play a role in many important facets of human physiology, from regulating blood pressure to intestinal fluid secretion. The structural mechanisms which influence these physiological processes have yet be explored. We present the 3.9 Å resolution cryo-EM structure membrane cyclase GC-C complex with Hsp90 and its co-chaperone Cdc37, providing insight into mechanism Cdc37 mediated binding regulatory complex. As protein non-kinase client Hsp90–Cdc37,...