scholarly journals Revealing the mechanism of repressor inactivation during switching of a temperate bacteriophage

2020 ◽  
Vol 117 (34) ◽  
pp. 20576-20585
Author(s):  
Kim Krighaar Rasmussen ◽  
Andrés Palencia ◽  
Anders K. Varming ◽  
Habiba El-Wali ◽  
Elisabetta Boeri Erba ◽  
...  
Keyword(s):  
Life Cycle ◽  
Solution Structure ◽  
Life Cycles ◽  
Relaxation Dispersion ◽  
Structural Basis ◽  
Human Pathogens ◽  
Sequence Alignments ◽  
Genetic Switch ◽  
Binding Interface

Temperate bacteriophages can enter one of two life cycles following infection of a sensitive host: the lysogenic or the lytic life cycle. The choice between the two alternative life cycles is dependent upon a tight regulation of promoters and their cognate regulatory proteins within the phage genome. We investigated the genetic switch of TP901-1, a bacteriophage ofLactococcus lactis, controlled by the CI repressor and the modulator of repression (MOR) antirepressor and their interactions with DNA. We determined the solution structure of MOR, and we solved the crystal structure of MOR in complex with the N-terminal domain of CI, revealing the structural basis of MOR inhibition of CI binding to the DNA operator sites.15N NMR Carr–Purcell–Meiboom–Gill (CPMG) relaxation dispersion and rotating frameR1ρmeasurements demonstrate that MOR displays molecular recognition dynamics on two different time scales involving a repacking of aromatic residues at the interface with CI. Mutations in the CI:MOR binding interface impair complex formation in vitro, and when introduced in vivo, the bacteriophage switch is unable to choose the lytic life cycle showing that the CI:MOR complex is essential for proper functioning of the genetic switch. On the basis of sequence alignments, we show that the structural features of the MOR:CI complex are likely conserved among a larger family of bacteriophages from human pathogens implicated in transfer of antibiotic resistance.

scholarly journals Solution structure of the autophagy-related protein LC3C reveals a polyproline II motif on a mobile tether with phosphorylation site

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Carsten Krichel ◽  
Christina Möckel ◽  
Oliver Schillinger ◽  
Pitter F. Huesgen ◽  
Heinrich Sticht ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Solution Structure ◽  
Phosphorylation Site ◽  
Backbone Dynamics ◽  
Dimensional Structure ◽  
High Sequence Identity ◽  
Amino Terminal ◽  
Polyproline Ii ◽  
Binding Interface

Abstract (Macro-)autophagy is a compartmental degradation pathway conserved from yeast to mammals. The yeast protein Atg8 mediates membrane tethering/hemifusion and cargo recruitment and is essential for autophagy. The human MAP1LC3/GABARAP family proteins show high sequence identity with Atg8, but MAP1LC3C is distinguished by a conspicuous amino-terminal extension with unknown functional significance. We have determined the high-resolution three-dimensional structure and measured the backbone dynamics of MAP1LC3C by NMR spectroscopy. From Ser18 to Ala120, MAP1LC3C forms an α-helix followed by the ubiquitin-like tertiary fold with two hydrophobic binding pockets used by MAP1LC3/GABARAP proteins to recognize targets presenting LC3-interacting regions (LIRs). Unlike other MAP1LC3/GABARAP proteins, the amino-terminal region of MAP1LC3C does not form a stable helix α1 but a “sticky arm” consisting of a polyproline II motif on a flexible linker. Ser18 at the interface between this linker and the structural core can be phosphorylated in vitro by protein kinase A, which causes additional conformational heterogeneity as monitored by NMR spectroscopy and molecular dynamics simulations, including changes in the LIR-binding interface. Based on these results we propose that the amino-terminal polyproline II motif mediates specific interactions with the microtubule cytoskeleton and that Ser18 phosphorylation modulates the interplay of MAP1LC3C with its various target proteins.

Structural basis for the sequestration of the anti-σ70factor Rsd from σ70by the histidine-containing phosphocarrier protein HPr

2015 ◽  
Vol 71 (10) ◽  
pp. 1998-2008 ◽  
Author(s):  
Young-Ha Park ◽  
Si-Hyeon Um ◽  
Saemee Song ◽  
Yeong-Jae Seok ◽  
Nam-Chul Ha
Keyword(s):  
Sigma Factor ◽  
Phosphorylation Site ◽  
Structural Basis ◽  
Coupled Transport ◽  
Phosphotransferase System ◽  
Binding Interface ◽  
Antisigma Factor ◽  
Sigma Subunit

Histidine-containing phosphocarrier protein (HPr) is a general component of the bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) involved in the phosphorylation-coupled transport of numerous sugars called PTS sugars. HPr mainly exists in a dephosphorylated form in the presence of PTS sugars in the medium, while its phosphorylation increases in the absence of PTS sugars. A recent study revealed that the dephosphorylated form of HPr binds and antagonizes the function of the antisigma factor Rsd. This anti-sigma factor sequesters the housekeeping sigma factor σ70to facilitate switching of the sigma subunit on RNA polymerase from σ70to the stress-responsive sigma factor σSin stationary-phase cells. In this study, the structure of the complex of Rsd and HPr was determined at 2.1 Å resolution and revealed that the binding site for HPr on the surface of Rsd partly overlaps with that for σ70. The localization of the phosphorylation site on HPr at the binding interface for Rsd explains why phosphorylation of HPr abolishes its binding to Rsd. The mutation of crucial residues involved in the HPr–Rsd interaction significantly influenced the competition between HPr and σ70for binding to Rsd bothin vitroandin vivo. The results provide a structural basis for the linkage of global gene regulation to nutrient availability in the external environment.

scholarly journals Domain-swapped Dimerization of the Second PDZ Domain of ZO2 May Provide a Structural Basis for the Polymerization of Claudins

2007 ◽  
Vol 282 (49) ◽  
pp. 35988-35999 ◽  
Author(s):  
Jiawen Wu ◽  
Yinshan Yang ◽  
Jiahai Zhang ◽  
Peng Ji ◽  
Wenjing Du ◽  
...  
Keyword(s):  
Solution Structure ◽  
Pdz Domain ◽  
Three Dimensional ◽  
Structural Basis ◽  
Pdz Domains ◽  
Zonula Occludens ◽  
Associated Proteins ◽  
High Conservation

Zonula occludens proteins (ZOs), including ZO1/2/3, are tight junction-associated proteins. Each of them contains three PDZ domains. It has been demonstrated that ZO1 can form either homodimers or heterodimers with ZO2 or ZO3 through the second PDZ domain. However, the underlying structural basis is not well understood. In this study, the solution structure of the second PDZ domain of ZO2 (ZO2-PDZ2) was determined using NMR spectroscopy. The results revealed a novel dimerization mode for PDZ domains via three-dimensional domain swapping, which can be generalized to homodimers of ZO1-PDZ2 or ZO3-PDZ2 and heterodimers of ZO1-PDZ2/ZO2-PDZ2 or ZO1-PDZ2/ZO3-PDZ2 due to high conservation between PDZ2 domains in ZO proteins. Furthermore, GST pulldown experiments and immunoprecipitation studies demonstrated that interactions between ZO1-PDZ2 and ZO2-PDZ2 and their self-associations indeed exist both in vitro and in vivo. Chemical cross-linking and dynamic laser light scattering experiments revealed that both ZO1-PDZ2 and ZO2-PDZ2 can form oligomers in solution. This PDZ domain-mediated oligomerization of ZOs may provide a structural basis for the polymerization of claudins, namely the formation of tight junctions.

Investigation of the morphological diversity of the potentially zoonoticTrypanosoma copemaniin quokkas and Gilbert's potoroos

Parasitology ◽  
2015 ◽  
Vol 142 (11) ◽  
pp. 1443-1452 ◽  
Author(s):  
JILL M. AUSTEN ◽  
SIMON A. REID ◽  
DERRICK R. ROBINSON ◽  
JAMES A. FRIEND ◽  
WILLIAM G. F. DITCHAM ◽  
...  
Keyword(s):  
Life Cycle ◽  
Severe Disease ◽  
Morphological Diversity ◽  
Blood Stream ◽  
Life Cycles ◽  
Clinical Effects ◽  
Life Cycle Stages ◽  
Normal Human

SUMMARYTrypanosomes are blood-borne parasites that can cause severe disease in both humans and animals, yet little is known of the pathogenicity and life-cycles of trypanosomes in native Australian mammals.Trypanosoma copemaniis known to be infective to a variety of Australian marsupials and has recently been shown to be potentially zoonotic as it is resistant to normal human serum. In the present study,in vivoandin vitroexamination of blood and cultures from Australian marsupials was conducted using light microscopy, immunofluorescence, scanning electron microscopy and fluorescencein situhybridization. Promastigote, sphaeromastigote and amastigote life-cycle stages were detectedin vivoandin vitro. Novel trypanosome-like stages were also detected bothin vivoandin vitrorepresenting an oval stage, an extremely thin stage, an adherent stage and a tiny round stage. The tiny round and adherent stages appeared to adhere to erythrocytes causing potential haematological damage with clinical effects similar to haemolytic anaemia. The present study shows for the first time that trypomastigotes are not the only life-cycle stages circulating within the blood stream of trypanosome infected Australian native marsupials and provides insights into possible pathogenic mechanisms of this potentially zoonotic trypanosome species.

scholarly journals Protein engineering expands the effector recognition profile of a rice NLR immune receptor

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Juan Carlos De la Concepcion ◽  
Marina Franceschetti ◽  
Dan MacLean ◽  
Ryohei Terauchi ◽  
Sophien Kamoun ◽  
...  
Keyword(s):  
Protein Engineering ◽  
Direct Interaction ◽  
Structural Basis ◽  
In Planta ◽  
Pathogen Effectors ◽  
Binding Interface ◽  
Pathogen Effector ◽  
Integrated Domains

Plant nucleotide binding, leucine-rich repeat (NLR) receptors detect pathogen effectors and initiate an immune response. Since their discovery, NLRs have been the focus of protein engineering to improve disease resistance. However, this approach has proven challenging, in part due to their narrow response specificity. Previously, we revealed the structural basis of pathogen recognition by the integrated heavy metal associated (HMA) domain of the rice NLR Pikp (Maqbool et al., 2015). Here, we used structure-guided engineering to expand the response profile of Pikp to variants of the rice blast pathogen effector AVR-Pik. A mutation located within an effector-binding interface of the integrated Pikp–HMA domain increased the binding affinity for AVR-Pik variants in vitro and in vivo. This translates to an expanded cell-death response to AVR-Pik variants previously unrecognized by Pikp in planta. The structures of the engineered Pikp–HMA in complex with AVR-Pik variants revealed the mechanism of expanded recognition. These results provide a proof-of-concept that protein engineering can improve the utility of plant NLR receptors where direct interaction between effectors and NLRs is established, particularly where this interaction occurs via integrated domains.

scholarly journals Structural basis for Scc3-dependent cohesin recruitment to chromatin

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Yan Li ◽  
Kyle W Muir ◽  
Matthew W Bowler ◽  
Jutta Metz ◽  
Christian H Haering ◽  
...  
Keyword(s):  
Dna Binding ◽  
Dna Interaction ◽  
Structural Basis ◽  
Binding Interface ◽  
Double Stranded Dna ◽  
Damage Repair ◽  
Chromatid Cohesion ◽  
Ring Complex ◽  
Positively Charged

The cohesin ring complex is required for numerous chromosomal transactions including sister chromatid cohesion, DNA damage repair and transcriptional regulation. How cohesin engages its chromatin substrate has remained an unresolved question. We show here, by determining a crystal structure of the budding yeast cohesin HEAT-repeat subunit Scc3 bound to a fragment of the Scc1 kleisin subunit and DNA, that Scc3 and Scc1 form a composite DNA interaction module. The Scc3-Scc1 subcomplex engages double-stranded DNA through a conserved, positively charged surface. We demonstrate that this conserved domain is required for DNA binding by Scc3-Scc1 in vitro, as well as for the enrichment of cohesin on chromosomes and for cell viability. These findings suggest that the Scc3-Scc1 DNA-binding interface plays a central role in the recruitment of cohesin complexes to chromosomes and therefore for cohesin to faithfully execute its functions during cell division.

scholarly journals A non-competing pair of human neutralizing antibodies block COVID-19 virus binding to its receptor ACE2

2020 ◽  
Author(s):  
Yan Wu ◽  
Feiran Wang ◽  
Chenguang Shen ◽  
Weiyu Peng ◽  
Delin Li ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Neutralizing Antibodies ◽  
Immune Escape ◽  
Structural Basis ◽  
Cellular Receptor ◽  
Virus Binding ◽  
Reduction Activity ◽  
Binding Interface ◽  
Neutralizing Capacity

AbstractNeutralizing antibodies could be antivirals against COVID-19 pandemics. Here, we report the isolation of four human-origin monoclonal antibodies from a convalescent patient in China. All of these isolated antibodies display neutralization abilities in vitro. Two of them (B38 and H4) block the binding between RBD and vial cellular receptor ACE2. Further competition assay indicates that B38 and H4 recognize different epitopes on the RBD, which is ideal for a virus-targeting mAb-pair to avoid immune escape in the future clinical applications. Moreover, therapeutic study on the mouse model validated that these two antibodies can reduce virus titers in the infected mouse lungs. Structure of RBD-B38 complex revealed that most residues on the epitope are overlapped with the RBD-ACE2 binding interface, which explained the blocking efficacy and neutralizing capacity. Our results highlight the promise of antibody-based therapeutics and provide the structural basis of rational vaccine design.One Sentence SummaryA pair of human neutralizing monoclonal antibodies against COVID-19 compete cellular receptor binding but with different epitopes, and with post-exposure viral load reduction activity.

scholarly journals The structural basis for dynamic DNA binding and bridging interactions which condense the bacterial centromere

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Gemma LM Fisher ◽  
César L Pastrana ◽  
Victoria A Higman ◽  
Alan Koh ◽  
James A Taylor ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Dna Binding ◽  
Dna Condensation ◽  
Structural Basis ◽  
Dna Binding Domain ◽  
Dynamic Nature ◽  
Terminal Domain ◽  
Binding Interface

The ParB protein forms DNA bridging interactions around parS to condense DNA and earmark the bacterial chromosome for segregation. The molecular mechanism underlying the formation of these ParB networks is unclear. We show here that while the central DNA binding domain is essential for anchoring at parS, this interaction is not required for DNA condensation. Structural analysis of the C-terminal domain reveals a dimer with a lysine-rich surface that binds DNA non-specifically and is essential for DNA condensation in vitro. Mutation of either the dimerisation or the DNA binding interface eliminates ParB-GFP foci formation in vivo. Moreover, the free C-terminal domain can rapidly decondense ParB networks independently of its ability to bind DNA. Our work reveals a dual role for the C-terminal domain of ParB as both a DNA binding and bridging interface, and highlights the dynamic nature of ParB networks in Bacillus subtilis.

scholarly journals Leishmania differentiation requires ubiquitin conjugation mediated by a UBC2-UEV1 E2 complex

2020 ◽  
Author(s):  
Rebecca J. Burge ◽  
Andreas Damianou ◽  
Anthony J. Wilkinson ◽  
Boris Rodenko ◽  
Jeremy C. Mottram
Keyword(s):  
Life Cycle ◽  
Crystal Structure Analysis ◽  
Structural Basis ◽  
Mammalian Host ◽  
Insect Vector ◽  
Post Translational Modification ◽  
Mouse Infection ◽  
Null Mutants

AbstractPost-translational modifications such as ubiquitination are important for orchestrating the cellular transformations that occur as the Leishmania parasite differentiates between its main morphological forms, the promastigote and amastigote. 2 E1 ubiquitin-activating (E1), 13 E2 ubiquitin-conjugating (E2), 79 E3 ubiquitin ligase (E3) and 20 deubiquitinating cysteine peptidase (DUB) genes can be identified in the Leishmania mexicana genome but, currently, little is known about the role of E1, E2 and E3 enzymes in this parasite. Bar-seq analysis of 23 E1, E2 and E3 null mutants generated in promastigotes using CRISPR-Cas9 revealed numerous loss-of-fitness phenotypes in promastigote to amastigote differentiation and mammalian infection. The E2s UBC1/CDC34, UBC2 and UEV1 and the HECT E3 ligase HECT2 are required for the successful transformation from promastigote to amastigote and UBA1b, UBC9, UBC14, HECT7 and HECT11 are required for normal proliferation during mouse infection. Null mutants could not be generated for the E1 UBA1a or the E2s UBC3, UBC7, UBC12 and UBC13, suggesting these genes are essential in promastigotes. X-ray crystal structure analysis of UBC2 and UEV1, orthologues of human UBE2N and UBE2V1/UBE2V2 respectively, reveal a heterodimer with a highly conserved interface, highlighting the importance of stable UBC2-UEV1 interaction in the function of this complex across diverse eukaryotes. Furthermore, recombinant L. mexicana E1 UBA1a can load ubiquitin onto UBC2, allowing UBC2-UEV1 to form K63-linked di-ubiquitin chains in vitro. Notably, UBC2 can also cooperate in vitro with human E3s RNF8 and BIRC2 to form non-K63-linked polyubiquitin chains, showing that UBC2 can facilitate ubiquitination independent of UEV1, but association of UBC2 with UEV1 inhibits this ability. Our study demonstrates the dual essentiality of UBC2 and UEV1 in the differentiation and intracellular survival of L. mexicana and shows that the interaction between these two proteins is crucial for regulation of their ubiquitination activity and function.Author summaryThe post-translational modification of proteins is key for allowing Leishmania parasites to transition between the different life cycle stages that exist in its insect vector and mammalian host. In particular, components of the ubiquitin system are important for the transformation of Leishmania from its insect (promastigote) to mammalian (amastigote) stage and normal infection in mice. However, little is known about the role of the enzymes that generate ubiquitin modifications in Leishmania. Here we characterise 28 enzymes of the ubiquitination pathway and show that many are required for life cycle progression or mouse infection by this parasite. Two proteins, UBC2 and UEV1, were selected for further study based on their importance in the promastigote to amastigote transition. We demonstrate that UBC2 and UEV1 form a heterodimer capable of carrying out ubiquitination and that the structural basis for this activity is conserved between Leishmania, Saccharomyces cerevisiae and humans. We also show that the interaction of UBC2 with UEV1 alters the nature of the ubiquitination activity performed by UBC2. Overall, we demonstrate the important role that ubiquitination enzymes play in the life cycle and infection process of Leishmania and explore the biochemistry underlying UBC2 and UEV1 function.

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