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The peptidoglycan (PG) layer is a critical component of the bacterial cell wall and serves as an important target for antibiotics in both gram-negative and gram-positive bacteria. The hydrolysis of septal PG (sPG) is a crucial step of bacterial cell division, facilitated by FtsEX through an amidase activation system. In this study, we present the cryo-EM structures of Escherichia coli FtsEX and FtsEX-EnvC in the ATP-bound state at resolutions of 3.05 Å and 3.11 Å, respectively. Our PG degradation assays in E. coli reveal that the ATP-bound conformation of FtsEX activates sPG hydrolysis of EnvC-AmiB, whereas EnvC-AmiB alone exhibits autoinhibition. Structural analyses indicate that ATP binding induces conformational changes in FtsEX-EnvC, leading to significant differences from the apo state. Furthermore, PG degradation assays of AmiB mutants confirm that the regulation of AmiB by FtsEX-EnvC is achieved through the interaction between EnvC-AmiB. These findings not only provide structural insight into the mechanism of sPG hydrolysis and bacterial cell division, but also have implications for the development of novel therapeutics targeting drug-resistant bacteria. The septal peptidoglycan hydrolysis machinery is a crucial structure for bacterial cell division. This study analyses the cryo-EM structure and enzymatic function of E. coli FtsEX, with and without the lytic-factor protein EnvC, characterizing the molecular basis of FtsEX regulation of peptidoglycan hydrolysis, which could be used to develop novel treatments targeting drug-resistant bacteria. [ABSTRACT FROM AUTHOR]

All Gram-negative bacteria, mitochondria and chloroplasts have outer membrane proteins (OMPs) that perform many fundamental biological processes. The OMPs in Gram-negative bacteria are inserted and folded into the outer membrane by the -barrel assembly machinery (BAM). The mechanism involved is poorly understood, owing to the absence of a structure of the entire BAM complex. Here we report two crystal structures of the Escherichia coli BAM complex in two distinct states: an inward-open state and a lateral-open state. Our structures reveal that the five polypeptide transport-associated domains of BamA form a ring architecture with four associated lipoproteins, BamBBamE, in the periplasm. Our structural, functional studies and molecular dynamics simulations indicate that these subunits rotate with respect to the integral membrane -barrel of BamA to induce movement of the -strands of the barrel and promote insertion of the nascent OMP., Author(s): Yinghong Gu [1]; Huanyu Li [1]; Haohao Dong [1]; Yi Zeng [1]; Zhengyu Zhang [1]; Neil G. Paterson [2]; Phillip J. Stansfeld [3]; Zhongshan Wang [1, 4, 5]; Yizheng [...]

Lipopolysaccharide (LPS) is essential for most Gram-negative bacteria and has crucial roles in protection of the bacteria from harsh environments and toxic compounds, including antibiotics. Seven LPS transport proteins (that is, LptA-LptG) form a trans-envelope protein complex responsible for the transport of LPS from the inner membrane to the outer membrane, the mechanism for which is poorly understood. Here we report the first crystal structure of the unique integral membrane LPS translocon LptD-LptE complex. LptD forms a novel 26- stranded β-barrel, which is to our knowledge the largest β-barrel reported so far. LptE adopts a roll-like structure located inside the barrel of LptD to form an unprecedented two-protein 'barrel and plug' architecture. The structure, molecular dynamics simulations and functional assays suggest that the hydrophilic O-antigen and the core oligosaccharide of the LPS may pass through the barrel and the lipid A of the LPS may be inserted into the outer leaflet of the outer membrane through a lateral opening between strands β1 and β26 of LptD. These findings not only help us to understand important aspects of bacterial outer membrane biogenesis, but also have significant potential for the development of novel drugs against multi-drug resistant pathogenic bacteria., All Gram-negative bacteria have an asymmetric outer membrane, in which the inner leaflet consists of phospholipid and the outer leaflet is comprised of lipopolysaccharide (LPS) (1,2). LPS normally has three [...]

Lassa virus, the causative agent of Lassa fever, causes thousands of deaths annually and is a biological threat agent, for which there is no vaccine and limited therapy. The nucleoprotein (NP) of Lassa virus has essential roles in viral RNA synthesis and immune suppression, the molecular mechanisms of which are poorly understood. Here we report the crystal structure of Lassa virus NP at 1.80 A resolution, which reveals amino (N)- and carboxy (C)-terminal domains with structures unlike any of the reported viral NPs. The N domain folds into a novel structure with a deep cavity for binding the m7GpppN cap structure that is required for viral RNA transcription, whereas the C domain contains 3'-5' exoribonuclease activity involved in suppressing interferon induction. To our knowledge this is the first X-ray crystal structure solved for an arenaviral NP, which reveals its unexpected functions and indicates unique mechanisms in cap binding and immune evasion. These findings provide great potential for vaccine and drug development., Several arenaviruses, including Lassa virus (LASV), can cause severe viral haemorrhagic fevers in humans with high morbidity and mortality, to which there is no vaccine and limited treatment (1-4). These [...]

Author(s): Changjiang Dong [1]; Fanglu Huang [2]; Hai Deng [1]; Christoph Schaffrath [1]; Jonathan B. Spencer [2]; David O'Hagan [1]; James H. Naismith (corresponding author) [1] Fluorine is the thirteenth [...]

Vibrio cholerae causes a severe disease that kills thousands of people annually. The outer membrane protein OmpU is the most abundant outer membrane protein in V. cholerae, and has been identified as an important virulence factor that is involved in host‐cell interaction and recognition, as well as being critical for the survival of the pathogenic V. cholerae in the host body and in harsh environments. The mechanism of these processes is not well understood owing to a lack of the structure of V. cholerae OmpU. Here, the crystal structure of the V. cholerae OmpU trimer is reported to a resolution of 2.2 Å. The protomer forms a 16‐β‐stranded barrel with a noncanonical N‐terminal coil located in the lumen of the barrel that consists of residues Gly32–Ser42 and is observed to participate in forming the second gate in the pore. By mapping the published functional data onto the OmpU structure, the OmpU structure reinforces the notion that the long extracellular loop L4 with a β‐hairpin‐like motif may be critical for host‐cell binding and invasion, while L3, L4 and L8 are crucially implicated in phage recognition by V. cholerae. [ABSTRACT FROM AUTHOR]