scholarly journals Cryo-EM structure of the full-length WzmWzt ABC transporter required for lipid-linked O antigen transport

2020 ◽  
Vol 118 (1) ◽  
pp. e2016144118
Author(s):  
Christopher A. Caffalette ◽  
Jochen Zimmer
Keyword(s):  
Cell Surface ◽  
Abc Transporter ◽  
Bound State ◽  
Binding Domain ◽  
Full Length ◽  
Carbohydrate Binding ◽  
Aquifex Aeolicus ◽  
O Antigen ◽  
Lipid Environment ◽  
O Antigens

O antigens are important cell surface polysaccharides in gram-negative bacteria where they extend core lipopolysaccharides in the extracellular leaflet of the outer membrane. O antigen structures are serotype specific and form extended cell surface barriers endowing many pathogens with survival benefits. In the ABC transporter-dependent biosynthesis pathway, O antigens are assembled on the cytosolic side of the inner membrane on a lipid anchor and reoriented to the periplasmic leaflet by the channel-forming WzmWzt ABC transporter for ligation to the core lipopolysaccharides. In many cases, this process depends on the chemical modification of the O antigen’s nonreducing terminus, sensed by WzmWzt via a carbohydrate-binding domain (CBD) that extends its nucleotide-binding domain (NBD). Here, we provide the cryo-electron microscopy structure of the full-length WzmWzt transporter fromAquifex aeolicusbound to adenosine triphosphate (ATP) and in a lipid environment, revealing a highly asymmetric transporter organization. The CBDs dimerize and associate with only one NBD. Conserved loops at the CBD dimer interface straddle a conserved peripheral NBD helix. The CBD dimer is oriented perpendicularly to the NBDs and its putative ligand-binding sites face the transporter to likely modulate ATPase activity upon O antigen binding. Further, our structure reveals a closed WzmWzt conformation in which an aromatic belt near the periplasmic channel exit seals the transporter in a resting, ATP-bound state. The sealed transmembrane channel is asymmetric, with one open and one closed cytosolic and periplasmic portal. The structure provides important insights into O antigen recruitment to and translocation by WzmWzt and related ABC transporters.

scholarly journals ABC Transporters Involved in Export of Cell Surface Glycoconjugates

2010 ◽  
Vol 74 (3) ◽  
pp. 341-362 ◽  
Author(s):  
Leslie Cuthbertson ◽  
Veronica Kos ◽  
Chris Whitfield
Keyword(s):  
Cell Surface ◽  
Abc Transporter ◽  
Abc Transporters ◽  
Nucleotide Binding ◽  
Binding Domain ◽  
Nucleotide Binding Domain ◽  
Polysaccharide Biosynthesis ◽  
O Antigens ◽  
And Function ◽  
Substrate Binding Domain

SUMMARY Complex glycoconjugates play critical roles in the biology of microorganisms. Despite the remarkable diversity in glycan structures and the bacteria that produce them, conserved themes are evident in the biosynthesis-export pathways. One of the primary pathways involves representatives of the ATP-binding cassette (ABC) transporter superfamily. These proteins are responsible for the export of a wide variety of cell surface oligo- and polysaccharides in both Gram-positive and Gram-negative bacteria. Recent investigations of the structure and function of ABC transporters involved in the export of lipopolysaccharide O antigens have revealed two fundamentally different strategies for coupling glycan polymerization to export. These mechanisms are distinguished by the presence (or absence) of characteristic nonreducing terminal modifications on the export substrates, which serve as chain termination and/or export signals, and by the presence (or absence) of a discrete substrate-binding domain in the nucleotide-binding domain polypeptide of the ABC transporter. A bioinformatic survey examining ABC exporters from known oligo- and polysaccharide biosynthesis loci identifies conserved nucleotide-binding domain protein families that correlate well with themes in the structures and assembly of glycans. The familial relationships among the ABC exporters generate hypotheses concerning the biosynthesis of structurally diverse oligo- and polysaccharides, which play important roles in the biology of bacteria with different lifestyles.

scholarly journals Identification of the Pseudomonas aeruginosa O17 and O15 O-Specific Antigen Biosynthesis Loci Reveals an ABC Transporter-Dependent Synthesis Pathway and Mechanisms of Genetic Diversity

2020 ◽  
Vol 202 (19) ◽  
Author(s):  
Steven M. Huszczynski ◽  
Youai Hao ◽  
Joseph S. Lam ◽  
Cezar M. Khursigara
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Abc Transporter ◽  
Specific Antigen ◽  
Opportunistic Pathogen ◽  
Content Type ◽  
O Antigen ◽  
O Antigens ◽  
Dependent Pathway

ABSTRACT Many bacterial cell surface glycans, such as the O antigen component of lipopolysaccharide (LPS), are produced via the so-called Wzx/Wzy- or ABC transporter-dependent pathways. O antigens are highly diverse polysaccharides that protect bacteria from their environment and engage in important host-pathogen interactions. The specific structure and composition of O antigens are the basis of classifying bacteria into O serotypes. In the opportunistic pathogen Pseudomonas aeruginosa, there are currently 20 known O-specific antigen (OSA) structures. The clusters of genes responsible for 18 of these O antigens have been identified, all of which follow the Wzx/Wzy-dependent pathway and are located at a common locus. In this study, we located the two unidentified O antigen biosynthesis clusters responsible for the synthesis of the O15 and the O17 OSA structures by analyzing published whole-genome sequence data. Intriguingly, these clusters were found outside the conserved OSA biosynthesis locus and were likely acquired through multiple horizontal gene transfer events. Based on data from knockout and overexpression studies, we determined that the synthesis of these O antigens follows an ABC transporter-dependent rather than a Wzx/Wzy-dependent pathway. In addition, we collected evidence to show that the O15 and O17 polysaccharide chain lengths are regulated by molecular rulers with distinct and variable domain architectures. The findings in this report are critical for a comprehensive understanding of O antigen biosynthesis in P. aeruginosa and provide a framework for future studies. IMPORTANCE P. aeruginosa is a problematic opportunistic pathogen that causes diseases in those with compromised host defenses, such as those suffering from cystic fibrosis. This bacterium produces a number of virulence factors, including a serotype-specific O antigen. Here, we identified and characterized the gene clusters that produce the O15 and O17 O antigens and show that they utilize a pathway for synthesis that is distinct from that of the 18 other known serotypes. We also provide evidence that these clusters have acquired mutations in specific biosynthesis genes and have undergone extensive horizontal gene transfer within the P. aeruginosa population. These findings expand on our understanding of O antigen biosynthesis in Gram-negative bacteria and the mechanisms that drive O antigen diversity.

scholarly journals Substrate recognition by a carbohydrate-binding module in the prototypical ABC transporter for lipopolysaccharide O-antigen from Escherichia coli O9a

2019 ◽  
Vol 294 (41) ◽  
pp. 14978-14990 ◽  
Author(s):  
Evan Mann ◽  
Steven D. Kelly ◽  
M. Sameer Al-Abdul-Wahid ◽  
Bradley R. Clarke ◽  
Olga G. Ovchinnikova ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Abc Transporter ◽  
Substrate Recognition ◽  
Carbohydrate Binding ◽  
Carbohydrate Binding Module ◽  
O Antigen

scholarly journals Identification of Carbohydrate-Binding Domains in the Attachment Proteins of Type 1 and Type 3 Reoviruses

2000 ◽  
Vol 74 (18) ◽  
pp. 8472-8479 ◽  
Author(s):  
James D. Chappell ◽  
Joy L. Duong ◽  
Benjamin W. Wright ◽  
Terence S. Dermody
Keyword(s):  
Sialic Acid ◽  
Cell Surface ◽  
Receptor Binding ◽  
Binding Domain ◽  
Carbohydrate Binding ◽  
Tail Domain ◽  
Amino Terminal ◽  
Binding Domains ◽  
Type 3

ABSTRACT The reovirus attachment protein, ς1, is responsible for strain-specific patterns of viral tropism in the murine central nervous system and receptor binding on cultured cells. The ς1 protein consists of a fibrous tail domain proximal to the virion surface and a virion-distal globular head domain. To better understand mechanisms of reovirus attachment to cells, we conducted studies to identify the region of ς1 that binds cell surface carbohydrate. Chimeric and truncated ς1 proteins derived from prototype reovirus strains type 1 Lang (T1L) and type 3 Dearing (T3D) were expressed in insect cells by using a baculovirus vector. Assessment of expressed protein susceptibility to proteolytic cleavage, binding to anti-ς1 antibodies, and oligomerization indicates that the chimeric and truncated ς1 proteins are properly folded. To assess carbohydrate binding, recombinant ς1 proteins were tested for the capacity to agglutinate mammalian erythrocytes and to bind sialic acid presented on glycophorin, the cell surface molecule bound by type 3 reovirus on human erythrocytes. Using a panel of two wild-type and ten chimeric and truncated ς1 proteins, the sialic acid-binding domain of type 3 ς1 was mapped to a region of sequence proposed to form the more amino terminal of two predicted β-sheet structures in the tail. This unit corresponds to morphologic region T(iii) observed in computer-processed electron micrographs of ς1 protein purified from virions. In contrast, the homologous region of T1L ς1 sequence was not implicated in carbohydrate binding; rather, sequences in the distal portion of the tail known as the neck were required. Results of these studies demonstrate that a functional receptor-binding domain, which uses sialic acid as its ligand, is contained within morphologic region T(iii) of the type 3 ς1 tail. Furthermore, our findings indicate that T1L and T3D ς1 proteins contain different arrangements of receptor-binding domains.

scholarly journals The carbohydrate-binding domain on galectin-1 is more extensive for a complex glycan than for simple saccharides: implications for galectin–glycan interactions at the cell surface

2009 ◽  
Vol 421 (2) ◽  
pp. 211-221 ◽  
Author(s):  
Michelle C. Miller ◽  
Irina V. Nesmelova ◽  
David Platt ◽  
Anatole Klyosov ◽  
Kevin H. Mayo
Keyword(s):  
Cell Surface ◽  
Quantum Coherence ◽  
Dissociation Constants ◽  
Lateral Diffusion ◽  
Binding Domain ◽  
Solution Viscosity ◽  
Carbohydrate Binding ◽  
Major Mode ◽  
Simple Carbohydrates ◽  
Complex Glycan

gal-1 (galectin-1) mediates cell–cell and cell–extracellular matrix adhesion, essentially by interacting with β-galactoside-containing glycans of cell-surface glycoconjugates. Although most structural studies with gal-1 have investigated its binding to simple carbohydrates, in particular lactose and N-acetyl-lactosamine, this view is limited, because gal-1 functions at the cell surface by interacting with more complex glycans that are heterogeneous in size and composition. In the present study we used NMR spectroscopy to investigate the interaction of human gal-1 with a large (120 kDa) complex glycan, GRG (galactorhamnogalacturonate glycan), that contains non-randomly distributed mostly terminal β(1→4)-linked galactose side chains. We used 15N–1H-HSQC (heteronuclear single quantum coherence) NMR experiments with 15N-enriched gal-1 to identify the GRG-binding region on gal-1 and found that this region covers a large surface area on gal-1 that includes the quintessential lactose-binding site and runs from that site through a broad valley or cleft towards the dimer interface. HSQC and pulsed-field-gradient NMR diffusion experiments also show that gal-1 binds GRG with a gal-1:GRG stoichiometry of about 5:1 (or 6:1) and with average macroscopic and microscopic equilibrium dissociation constants (Kd) of 8×10−6 M and 40×10−6 M (or 48×10−6 M) respectively, indicating stronger binding than to lactose (Kd=520×10−6 M). Although gal-1 may bind GRG in various ways, the glycan can be competed for by lactose, suggesting that there is one major mode of interaction. Furthermore, even though terminal motifs on GRG are Gal-β(1→4)-Gal rather than the traditional Gal-β(1→4)-Glc/GlcNAc (where GlcNAc is N-acetylglucosamine), we show that the disaccharide Gal-β(1→4)-Gal can bind gal-1 at the lactose-binding domain. In addition, gal-1 binding to GRG disrupts inter-glycan interactions and decreases glycan-mediated solution viscosity, a glycan decongestion effect that may help explain why gal-1 promotes membrane fluidity and lateral diffusion of glycoconjugates within cell membranes. Overall, our results provide an insight into the function of galectin in situ and have potential significant biological consequences.

scholarly journals Backbone NMR assignment of the nucleotide binding domain of the Bacillus subtilis ABC multidrug transporter BmrA in the post-hydrolysis state

2022 ◽  
Author(s):  
Victor Hugo Pérez Carrillo ◽  
Dania Rose-Sperling ◽  
Mai Anh Tran ◽  
Christoph Wiedemann ◽  
Ute A. Hellmich
Keyword(s):  
Bacillus Subtilis ◽  
Abc Transporter ◽  
Transmembrane Domain ◽  
Molecular Motor ◽  
Nucleotide Binding ◽  
Bound State ◽  
Binding Domain ◽  
Nucleotide Binding Domain ◽  
Backbone Chemical Shift ◽  
Nucleotide Interactions

AbstractATP binding cassette (ABC) proteins are present in all phyla of life and form one of the largest protein families. The Bacillus subtilis ABC transporter BmrA is a functional homodimer that can extrude many different harmful compounds out of the cell. Each BmrA monomer is composed of a transmembrane domain (TMD) and a nucleotide binding domain (NBD). While the TMDs of ABC transporters are sequentially diverse, the highly conserved NBDs harbor distinctive conserved motifs that enable nucleotide binding and hydrolysis, interdomain communication and that mark a protein as a member of the ABC superfamily. In the catalytic cycle of an ABC transporter, the NBDs function as the molecular motor that fuels substrate translocation across the membrane via the TMDs and are thus pivotal for the entire transport process. For a better understanding of the structural and dynamic consequences of nucleotide interactions within the NBD at atomic resolution, we determined the 1H, 13C and 15N backbone chemical shift assignments of the 259 amino acid wildtype BmrA-NBD in its post-hydrolytic, ADP-bound state.

scholarly journals Molluscum Contagiosum Virus Interleukin-18 (IL-18) Binding Protein Is Secreted as a Full-Length Form That Binds Cell Surface Glycosaminoglycans through the C-Terminal Tail and a Furin-Cleaved Form with Only the IL-18 Binding Domain

2003 ◽  
Vol 77 (4) ◽  
pp. 2623-2630 ◽  
Author(s):  
Yan Xiang ◽  
Bernard Moss
Keyword(s):  
Cell Surface ◽  
Binding Protein ◽  
Molluscum Contagiosum ◽  
Binding Domain ◽  
Full Length ◽  
Interleukin 18 ◽  
Molluscum Contagiosum Virus ◽  
Homologous Proteins ◽  
Furin Cleavage ◽  
Furin Cleavage Site

ABSTRACT Some poxviruses and their mammalian hosts encode homologous proteins that bind interleukin-18 (IL-18) with high affinity and inhibit IL-18-mediated immune responses. MC54L, the IL-18 binding protein of the human poxvirus that causes molluscum contagiosum, is unique in having a C-terminal tail of nearly 100 amino acids that is dispensable for IL-18 binding. When recombinant MC54L was expressed and purified via a C-terminal six-histidine tag, a shorter fragment was detected in addition to the full-length protein. This C-terminal fragment resulted from the cleavage of MC54L by cellular furin, as it was greatly diminished when furin was specifically inhibited or when a furin-deficient cell line was used for expression. Furthermore, the N- and C-terminal fragments of MC54L were generated by cleavage of the recombinant protein with furin in vitro. The furin cleavage site was mapped within a 32-amino-acid segment that is C terminal to the IL-18 binding domain. Full-length MC54L, but not the N-terminal IL-18 binding fragment, bound to cells and to purified heparin and other glycosaminoglycans that are commonly found on the cell surface and in the extracellular matrix. MC54L bound to heparin with a nanomolar Kd and could simultaneously bind to IL-18. Their different glycosaminoglycan and cell binding properties may allow the long and short forms of MC54L to inactivate IL-18 near the site of infection and at more distal locations, respectively.

scholarly journals lfnA from Pseudomonas aeruginosa O12 and wbuX from Escherichia coli O145 Encode Membrane-Associated Proteins and Are Required for Expression of 2,6-Dideoxy-2-Acetamidino-l-Galactose in Lipopolysaccharide O Antigen

2007 ◽  
Vol 190 (5) ◽  
pp. 1671-1679 ◽  
Author(s):  
Jerry D. King ◽  
Erin F. Mulrooney ◽  
Evgeny Vinogradov ◽  
Bernd Kneidinger ◽  
Kristen Mead ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Cell Surface ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Opportunistic Pathogen ◽  
Multidrug Resistant ◽  
Nuclear Magnetic Resonance Analysis ◽  
O Antigen ◽  
O Antigens

ABSTRACT The rare sugar 2,6-dideoxy-2-acetamidino-l-galactose (l-FucNAm) is found only in bacteria and is a component of cell surface glycans in a number of pathogenic species, including the O antigens of Pseudomonas aeruginosa serotype O12 and Escherichia coli O145. P. aeruginosa is an important opportunistic pathogen, and the O12 serotype is associated with multidrug-resistant epidemic outbreaks. O145 is one of the classic non-O157 serotypes associated with Shiga toxin-producing, enterohemorrhagic E. coli. The acetamidino (NAm) moiety of l-FucNAm is of interest, because at neutral pH it contributes a positive charge to the cell surface, and we aimed to characterize the biosynthesis of this functional group. The pathway is not known, but expression of NAm-modified sugars coincides with the presence of a pseA homologue in the relevant biosynthetic locus. PseA is a putative amidotransferase required for synthesis of a NAm-modified sugar in Campylobacter jejuni. In P. aeruginosa O12 and E. coli O145, the pseA homologues are lfnA and wbuX, respectively, and we hypothesized that these genes function in l-FucNAm biosynthesis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blotting, and nuclear magnetic resonance analysis of the lfnA mutant O-antigen structure indicated that the mutant expresses 2,6-dideoxy-2-acetamido-l-galactose (l-FucNAc) in place of l-FucNAm. The mutation could be complemented by expression of either His6-tagged lfnA or wbuX in trans, confirming that these genes are functional homologues and that they are required for NAm moiety synthesis. Both proteins retained their activity when fused to a His6 tag and localized to the membrane fraction. These data will assist future biochemical investigation of this pathway.

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