1
|
Liston SD, Ovchinnikova OG, Kimber MS, Whitfield C. A dedicated C-6 β-hydroxyacyltransferase required for biosynthesis of the glycolipid anchor for Vi antigen capsule in typhoidal Salmonella. J Biol Chem 2022; 298:102520. [PMID: 36152747 DOI: 10.1016/j.jbc.2022.102520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 09/15/2022] [Accepted: 09/16/2022] [Indexed: 11/17/2022] Open
Abstract
Vi antigen is an extracellular polysaccharide produced by Salmonella enterica Typhi, Citrobacter freundii, and some soil bacteria belonging to the Burkholderiales. In Salmonella Typhi, Vi-antigen capsule protects the bacterium against host defenses, and the glycan is used in a current glycoconjugate vaccine to protect against typhoid. Vi antigen is a glycolipid assembled in the cytoplasm and translocated to the cell surface by an export complex driven by an ABC transporter. In Salmonella Typhi, efficient export and cell-surface retention of the capsule layer depend on a reducing terminal acylated-HexNAc moiety. Although the precise structure and biosynthesis of the acylated terminus has not been resolved, it distinguishes Vi antigen from other known glycolipid substrates for bacterial ABC transporters. The genetic locus for Vi antigen-biosynthesis encodes a single acyltransferase candidate (VexE), which is implicated in the acylation process. Here, we determined the structure of the VexE in vitro reaction product by mass spectrometry and nuclear magnetic resonance spectroscopy, to reveal that VexE catalyzes β-hydroxyacyl-ACP dependent acylation of the activated sugar precursor, uridine-5'-diphospho-N-acetylglucosamine (UDP-GlcNAc), at C-6 to form UDP-6-O-[β-hydroxymyristoyl]-α-d-GlcNAc. VexE belongs to the lysophosphatidyl acyltransferase (LPLAT) family, and comparison of an Alphafold VexE model to solved LPLAT structures, together with modeling enzyme:substrate complexes, led us to predict an enzyme mechanism. This study provides new insight into Vi terminal structure, offers a new model substrate to investigate the mechanism of glycolipid ABC transporters, and adds biochemical understanding for a novel reaction used in synthesis of an important bacterial virulence factor.
Collapse
Affiliation(s)
- S D Liston
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - O G Ovchinnikova
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - M S Kimber
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - C Whitfield
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
| |
Collapse
|
2
|
Hamilton E, Hoskins H, Whitfield C, Helme D. P.28 Midwifery confidence in intrapartum epidural neurological monitoring: a survey and interventions. Int J Obstet Anesth 2022. [DOI: 10.1016/j.ijoa.2022.103324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
3
|
Hamilton E, Hoskins H, Whitfield C, Helme D. P.138 Monitoring of neurological blockade after epidural insertion on delivery suite. Int J Obstet Anesth 2022. [DOI: 10.1016/j.ijoa.2022.103434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
4
|
Whitfield C, Harris C. P.51 Obstetric anaesthetics database, dashboard and information dissemination. Int J Obstet Anesth 2022. [DOI: 10.1016/j.ijoa.2022.103347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
5
|
Totti S, Kluxen F, Toner F, Page L, Maas W, Webbley K, Nagane R, Valentine C, Kendrick J, Mingoia R, Whitfield C, Dorange J, Egron C, Imart C, Felkers E, Domoradzki J, Darraji B, McEuen S, Fisher P, Lorez C, Parr-Dobrzanksi R, Chen T, Wiemann C. An in vitro dermal absorption study ring trial with 14C-Caffeine according to OECD test guideline 428. Toxicol Lett 2021. [DOI: 10.1016/s0378-4274(21)00816-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
6
|
Whitfield C, Adamson M, Davies R. The effect of coincidental SARS-CoV-2 infection on pre-operative cardiopulmonary exercise testing. Anaesth Rep 2021; 9:122-126. [PMID: 34142086 PMCID: PMC8188990 DOI: 10.1002/anr3.12124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/2021] [Indexed: 11/11/2022] Open
Abstract
This case report demonstrates the significant impact active infection with SARS-CoV-2 can have on functional capacity evaluated by cardiopulmonary exercise testing, even in minimally symptomatic individuals. A 75-year-old man underwent cardiopulmonary exercise testing before a right hemicolectomy; SARS-CoV-2 was incidentally diagnosed following his test. The patient underwent a period of isolation and recovery before a second pre-operative cardiopulmonary exercise test 6 weeks later. His resting pulmonary function tests did not vary between tests but his peak work, anaerobic threshold, oxygen pulse, pulse oximetry nadir, ventilation perfusion matching and heart rate response to exercise all improved significantly after this recovery period. These are unique results that add to the existing knowledge of the pathophysiology and management of SARS-CoV-2 in the peri-operative setting. While our patient demonstrated dramatic improvement in his functional capacity following 6 weeks of recovery, he remained in a high-risk group for surgery according to our local guidelines. Cardiopulmonary exercise testing has a valuable role in individualised risk assessment and shared decision-making in complex, urgent surgical cases where the benefits of delaying surgery to recover from SARS-CoV-2 infection should be balanced against the potential risks.
Collapse
Affiliation(s)
- C Whitfield
- Department of Anaesthesia University Hospital of Wales Cardiff UK
| | - M Adamson
- Department of Anaesthesia University Hospital of Wales Cardiff UK
| | - R Davies
- Department of Anaesthesia University Hospital of Wales Cardiff UK
| |
Collapse
|
7
|
DeSouza K, Zammit R, Simpson L, Watson L, Bracewell K, Whitfield C, Bloomfield D, Simcock R, Sinha R, Westwell S, Moss C, Moss A, Sham J, Patel G. Defining the Older Patient Population (>65 Years) Treated for Metastatic Breast Cancer (mBC) Within the Sussex Cancer Network. Clin Oncol (R Coll Radiol) 2018. [DOI: 10.1016/j.clon.2018.02.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
|
8
|
Kelly R, Perry M, MacLean L, Whitfield C. Structures of the O-antigens of Klebsiella serotypes 02 (2a,2e), 02 (2a,2e,2h), and 02 (2a,2f,2g), members of a family of related D-galactan O-antigens in Klebsiella spp. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/096805199500200208] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The structures of the lipopolysaccharide O-antigens from Klebsiella serotypes 02(2a,2f,2g), O2(2a,2e) and O2(2a,2e,2h) have been determined. These O-polysaccharides are part of a family of related structures, which share a D-galactan I backbone. D-galactan I has the repeating unit structure: [→3)-β-D-Gal f-(1→3)-α-D-Gal p-(1→]. The O-polysaccharide of serotype O2(2a,2f,2g) differs from other known O-polysaccharides in Klebsiella spp. Each of the main-chain Gal p residues in the 02(2a,2f,2g) O-polysaccharide is substituted with an α-(1→4)-linked D-Gal p residue, to form a trisaccharide repeating unit. The LPS O-polysaccharides of serotypes O2(2a,2e) and O2(2a,2e,2h) both contain α-(1→2)-linked D-Galp substituents on the main-chain Galp residues, and resemble serotype O9. The only difference between the 09, O2(2a,2e), and O2(2a,2e,2h) carbohydrate structures involves the stoichiometry of addition of side chain α-D-Gal p residues. However, the polymers from serotypes O2(2a,2e), O2(2a,2e,2h) and 09 are all modified by O-acetylation and these modifications may contribute to altered antigenic factors. The structures reported here resolve ambiguities between previous chemical and serological analyses of 02 antigens. Genetic analyses showed that enzymes involved in the addition of α-D-Gal p residues are encoded by genes outside the rfbO9 (O-antigen biosynthesis) region and this provides an explanation for occasional non-stoichiometric addition of side chain α-D-Galp residues.
Collapse
Affiliation(s)
- R.F. Kelly
- Canadian Bacterial Diseases Network, Department of Microbiology, University of Guelph, Guelph, Ontario, Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario, Canada
| | - M.B. Perry
- Canadian Bacterial Diseases Network, Department of Microbiology, University of Guelph, Guelph, Ontario, Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario, Canada
| | - L.L. MacLean
- Canadian Bacterial Diseases Network, Department of Microbiology, University of Guelph, Guelph, Ontario, Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario, Canada
| | - C. Whitfield
- Canadian Bacterial Diseases Network, Department of Microbiology, University of Guelph, Guelph, Ontario, Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario, Canada
| |
Collapse
|
9
|
Whitfield C, Rodgers S. P2.026 Audit of Adherence to UK National Guideline For Management of Epididymo-Orchitis. Br J Vener Dis 2013. [DOI: 10.1136/sextrans-2013-051184.0291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
|
10
|
Carmichael RJ, Whitfield C, Maxwell LK. Pharmacokinetics of ganciclovir and valganciclovir in the adult horse. J Vet Pharmacol Ther 2013; 36:441-9. [PMID: 23301502 DOI: 10.1111/jvp.12029] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 11/02/2012] [Indexed: 11/29/2022]
Abstract
Equine herpes myeloencephalopathy, resulting from equine herpes virus type 1 (EHV-1) infection, is associated with substantial morbidity and mortality in the horse. As compared to other antiviral drugs, such as acyclovir, ganciclovir has enhanced potency against EHV-1. This study investigated the pharmacokinetics of ganciclovir and its oral prodrug, valganciclovir, in six adult horses in a randomized cross-over design. Ganciclovir sodium was administered intravenously as a slow bolus at a dose of 2.5 mg/kg, and valganciclovir was administered orally at a dose of 1800 mg per horse. Intravenously administered ganciclovir disposition was best described by a three-compartment model with a prolonged terminal half-life of 72 ± 9 h. Following the oral administration of valganciclovir, the mean observed maximum serum ganciclovir concentration was 0.58 ± 0.37 μg/mL, and bioavailability of ganciclovir from oral valganciclovir was 41 ± 20%. Superposition predicted that oral dosing of 1800-mg valganciclovir two times daily would fail to produce and maintain effective plasma concentrations of ganciclovir. However, superposition suggested that i.v. administration of ganciclovir at 2.5 mg/kg every 8 h for 24 h followed by maintenance dosing of 2.5 mg/kg every 12 h would maintain effective ganciclovir serum concentrations in most horses throughout the dosing interval.
Collapse
Affiliation(s)
- R J Carmichael
- Department of Veterinary Clinical Sciences, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK, USA
| | | | | |
Collapse
|
11
|
Bardsley K, Whitfield C. Targeting a Hard to Access Population—Heart Failure and Homelessness in Sydney. Heart Lung Circ 2012. [DOI: 10.1016/j.hlc.2012.05.237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
12
|
Troy FA, Adams DA, Whitfield C. Lipid Dynamics during the Spontaneous Reactivation of a Membranous Sialyltransferase Complex in Escherichia Coli K-235. Biophys J 2010; 37:85-6. [PMID: 19431516 DOI: 10.1016/s0006-3495(82)84612-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
|
13
|
Heyman J, Whitfield C, McCaughan G, Donaghy A. The impact of branch chain amino acid supplementation on body composition in cirrhosis. Nutrition 2008. [DOI: 10.1016/j.nut.2008.01.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
14
|
Whitfield C. Gelatin colloids in the resuscitation of trauma. J ROY ARMY MED CORPS 2007; 152:197-201. [PMID: 17508637 DOI: 10.1136/jramc-152-04-01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
To date, the specific role of gelatins in trauma resuscitation remains under-investigated. Their adverse affects are well described and relate principally to the provocation of allergic responses whilst their influence upon haemostasis is relatively benign in comparison to the other colloids. However, their benefits are only sparsely documented and the evidence to choose one gelatin over another virtually non-existent. As knowledge of the microcirculatory dysfunction inherent in the shocked state increases, the role of the gelatins in trauma resuscitation is being increasing sidelined by other colloids--notably the starches. Their role beyond a basic resuscitation tool is now uncertain.
Collapse
|
15
|
Dong C, Beis K, Giraud MF, Blankenfeldt W, Allard S, Major LL, Kerr ID, Whitfield C, Naismith JH. A structural perspective on the enzymes that convert dTDP-d-glucose into dTDP-l-rhamnose. Biochem Soc Trans 2003; 31:532-6. [PMID: 12773151 DOI: 10.1042/bst0310532] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Bacteria have a rich collection of biochemical pathways for the synthesis of complex metabolites. These conversions often involve chemical reactions that are hard to reproduce in the laboratory. An area of considerable interest is in the manipulation and synthesis of carbohydrates. In contrast with amino acids, carbohydrates are densely functionalized (each carbon atom is attached to at least one heteroatom) and this holds out the prospect of discovering novel enzyme mechanisms. The results from the study of the biosynthetic dTDP-L-rhamnose pathway are discussed. dTDP-L-rhamnose is a key intermediate in many pathogenic bacteria, as it is the donor for L-rhamnose, which is found in the cell wall of important human pathogens, such as Mycobacteria tuberculosis and Salmonella typhimurium. All four enzymes have been structurally characterized; in particular, the acquisition of structural data on substrate complexes was extremely useful. The structural data have guided site-directed-mutagenesis studies that have been used to test mechanistic hypotheses. The results shed light on three classes of enzyme mechanism: nucleotide condensation, short-chain dehydrogenase activity and epimerization.
Collapse
Affiliation(s)
- C Dong
- Centre for Biomolecular Science, The University, St. Andrews KY16 9ST, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Sanders DA, Staines AG, McMahon SA, McNeil MR, Whitfield C, Naismith JH. UDP-galactopyranose mutase has a novel structure and mechanism. Nat Struct Biol 2001; 8:858-63. [PMID: 11573090 DOI: 10.1038/nsb1001-858] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Uridine diphosphogalactofuranose (UDP-Galf ) is the precursor of the d-galactofuranose (Galf ) residues found in bacterial and parasitic cell walls, including those of many pathogens, such as Mycobacterium tuberculosis and Trypanosoma cruzi. UDP-Galf is made from UDP-galactopyranose (UDP-Galp) by the enzyme UDP-galactopyranose mutase (mutase). The mutase enzyme is essential for the viability of mycobacteria and is not found in humans, making it a viable therapeutic target. The mechanism by which mutase achieves the unprecedented ring contraction of a nonreducing sugar is unclear. We have solved the crystal structure of Escherichia coli mutase to 2.4 A resolution. The novel structure shows that the flavin nucleotide is located in a cleft lined with conserved residues. Site-directed mutagenesis studies indicate that this cleft contains the active site, with the sugar ring of the substrate UDP-galactose adjacent to the exposed isoalloxazine ring of FAD. Assay results establish that the enzyme is active only when flavin is reduced. We conclude that mutase most likely functions by transient reduction of substrate.
Collapse
Affiliation(s)
- D A Sanders
- The Centre for Biomolecular Sciences, The University, St. Andrews, Scotland KY16 9ST, UK
| | | | | | | | | | | |
Collapse
|
17
|
|
18
|
Yethon JA, Whitfield C. Lipopolysaccharide as a target for the development of novel therapeutics in gram-negative bacteria. Curr Drug Targets Infect Disord 2001; 1:91-106. [PMID: 12455407 DOI: 10.2174/1568005014606143] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Lipopolysaccharide (LPS) constitutes the lipid portion of the outer leaflet of Gram-negative bacteria, and is essential for growth. LPS is also known to be responsible for the variety of biological effects associated with Gram-negative sepsis. In recent years, tremendous progress has been made in determining the exact chemical structure of this highly complex macromolecule, and recent advances have elucidated much of the enzymology involved in its biosynthesis. Using this knowledge, a number of inhibitors to LPS biosynthesis have been developed: some of these compounds have antibacterial properties, while others show excellent in vitro activity and are undergoing further investigation. This review summarizes the main features of LPS structure, function, and biosynthesis, highlighting the potential target reactions that have been or might be exploited for therapeutic intervention.
Collapse
Affiliation(s)
- J A Yethon
- Department of Microbiology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | | |
Collapse
|
19
|
Guan S, Clarke AJ, Whitfield C. Functional analysis of the galactosyltransferases required for biosynthesis of D-galactan I, a component of the lipopolysaccharide O1 antigen of Klebsiella pneumoniae. J Bacteriol 2001; 183:3318-27. [PMID: 11344139 PMCID: PMC99629 DOI: 10.1128/jb.183.11.3318-3327.2001] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
D-Galactan I is an O-antigenic polymer with the repeat unit structure [-->3)-beta-D-Galf-(1-->3)-alpha-D-Galp-(1-->], that is found in the lipopolysaccharide of Klebsiella pneumoniae O1 and other gram-negative bacteria. A genetic locus containing six genes is responsible for the synthesis and assembly of D-galactan I via an ATP-binding cassette (ABC) transporter-dependent pathway. The galactosyltransferase activities that are required for the processive polymerization of D-galactan I were identified by using in vitro reactions. The activities were determined with endogenous lipid acceptors in membrane preparations from Escherichia coli K-12 expressing individual enzymes (or combinations of enzymes) or in membranes reconstituted with specific lipid acceptors. The D-galactan I polymer is built on a lipid acceptor, undecaprenyl pyrophosphoryl-GlcpNAc, a product of the WecA enzyme that participates in the biosynthesis of enterobacterial common antigen and O-antigenic polysaccharide (O-PS) biosynthesis pathways. This intermediate is directed into D-galactan I biosynthesis by the bifunctional wbbO gene product, which sequentially adds one Galp and one Galf residue from the corresponding UDP-sugars to form a lipid-linked trisaccharide. The two galactosyltransferase activities of WbbO are separable by limiting the UDP-Galf precursor. Galactosyltransferase activity in membranes reconstituted with exogenous lipid-linked trisaccharide acceptor and the known structure of D-galactan I indicate that WbbM catalyzes the subsequent transfer of a single Galp residue to form a lipid-linked tetrasaccharide. Chain extension of the D-galactan I polymer requires WbbM for Galp transferase, together with Galf transferase activity provided by WbbO. Comparison of the biosynthetic pathways for D-galactan I and the polymannose E. coli O9a antigen reveals some interesting features that may reflect a common theme in ABC transporter-dependent O-PS assembly systems.
Collapse
Affiliation(s)
- S Guan
- Department of Microbiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | | | | |
Collapse
|
20
|
Allard ST, Giraud MF, Whitfield C, Graninger M, Messner P, Naismith JH. The crystal structure of dTDP-D-Glucose 4,6-dehydratase (RmlB) from Salmonella enterica serovar Typhimurium, the second enzyme in the dTDP-l-rhamnose pathway. J Mol Biol 2001; 307:283-95. [PMID: 11243820 DOI: 10.1006/jmbi.2000.4470] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
l-Rhamnose is a 6-deoxyhexose that is found in a variety of different glycoconjugates in the cell walls of pathogenic bacteria. The precursor of l-rhamnose is dTDP-l-rhamnose, which is synthesised from glucose- 1-phosphate and deoxythymidine triphosphate (dTTP) via a pathway requiring four enzymes. Significantly this pathway does not exist in humans and all four enzymes therefore represent potential therapeutic targets. dTDP-D-glucose 4,6-dehydratase (RmlB; EC 4.2.1.46) is the second enzyme in the dTDP-L-rhamnose biosynthetic pathway. The structure of Salmonella enterica serovar Typhimurium RmlB had been determined to 2.47 A resolution with its cofactor NAD(+) bound. The structure has been refined to a crystallographic R-factor of 20.4 % and an R-free value of 24.9 % with good stereochemistry.RmlB functions as a homodimer with monomer association occurring principally through hydrophobic interactions via a four-helix bundle. Each monomer exhibits an alpha/beta structure that can be divided into two domains. The larger N-terminal domain binds the nucleotide cofactor NAD(+) and consists of a seven-stranded beta-sheet surrounded by alpha-helices. The smaller C-terminal domain is responsible for binding the sugar substrate dTDP-d-glucose and contains four beta-strands and six alpha-helices. The two domains meet to form a cavity in the enzyme. The highly conserved active site Tyr(167)XXXLys(171) catalytic couple and the GlyXGlyXXGly motif at the N terminus characterise RmlB as a member of the short-chain dehydrogenase/reductase extended family. The quaternary structure of RmlB and its similarity to a number of other closely related short-chain dehydrogenase/reductase enzymes have enabled us to propose a mechanism of catalysis for this important enzyme.
Collapse
Affiliation(s)
- S T Allard
- Centre for Biomolecular Sciences, The University, North Haugh, St Andrews Fife, KY16 9ST, Scotland
| | | | | | | | | | | |
Collapse
|
21
|
Yethon JA, Whitfield C. Purification and characterization of WaaP from Escherichia coli, a lipopolysaccharide kinase essential for outer membrane stability. J Biol Chem 2001; 276:5498-504. [PMID: 11069912 DOI: 10.1074/jbc.m008255200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In Escherichia coli, Salmonella enterica, and Pseudomonas aeruginosa, the waaP (rfaP) gene product is required for the addition of phosphate to O-4 of the first heptose residue of the lipopolysaccharide (LPS) inner core region. This phosphate substitution is particularly important to the biology of these bacteria; it has previously been shown that WaaP is necessary for resistance to hydrophobic and polycationic antimicrobials in E. coli and that it is required for virulence in invasive strains of S. enterica. WaaP function is also known to be essential for the viability of P. aeruginosa. The predicted WaaP protein shows low levels of similarity (10-15% identity) to eukaryotic protein kinases, but its kinase activity has never been tested. Here we report the purification of WaaP and the reconstitution of its enzymatic activity in vitro. The purified enzyme catalyzes the incorporation of 33P from [gamma-33P]ATP into acceptor LPS purified from a defined E. coli waaP mutant. Enzymatic activity is dependent upon the presence of Mg2+ and is maximal from pH 8.0 to 9.0. The apparent Km (determined at saturating concentrations of the second substrate) is 0.13 mm for ATP and 76 microm for LPS. These data are the first proof that WaaP is indeed an LPS kinase. Further, site-directed mutagenesis of a predicted catalytic residue suggests that WaaP shares a common mechanism of action with eukaryotic protein kinases.
Collapse
Affiliation(s)
- J A Yethon
- Department of Microbiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | | |
Collapse
|
22
|
Wugeditsch T, Paiment A, Hocking J, Drummelsmith J, Forrester C, Whitfield C. Phosphorylation of Wzc, a tyrosine autokinase, is essential for assembly of group 1 capsular polysaccharides in Escherichia coli. J Biol Chem 2001; 276:2361-71. [PMID: 11053445 DOI: 10.1074/jbc.m009092200] [Citation(s) in RCA: 158] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Wzc proteins are tyrosine autokinases. They are found in some important bacterial pathogens of humans and livestock as well as plant-associated bacteria, and are often encoded within gene clusters determining synthesis and assembly of capsular and extracellular polysaccharides. Autophosphorylation of Wzc(cps) is essential for assembly of the serotype K30 group 1 capsule in Escherichia coli O9a:K30, although a genetically unlinked Wzc(cps)-homologue (Etk) can also participate with low efficiency. While autophosphorylation of Wzc(cps) is required for assembly of high molecular weight K30 capsular polysaccharide, it is not essential for either the synthesis of the K30 repeat units or for activity of the K30 polymerase enzyme. Paradoxically, the cognate phosphotyrosine protein phosphatase for Wzc(cps), Wzb(cps), is also required for capsule expression. The tyrosine-rich domain at the C terminus of Wzc(cps) was identified as the site of phosphorylation and autophosphorylation of Wzc requires a functional Walker A motif. Intermolecular transphosphorylation of Wzc(cps) was detected in strains expressing a combination of mutant Wzc(cps) derivatives. The N- and C-terminal domains of Wzc(cps) were expressed independently to mimic the situation found naturally in Gram-positive bacteria. In this format, both domains were required for phosphorylation of the Wzc(cps) C terminus, and for capsule assembly. Regulation by a post-translational phosphorylation event represents a new dimension in the assembly of bacterial cell-surface polysaccharides.
Collapse
Affiliation(s)
- T Wugeditsch
- Department of Microbiology, University of Guelph, Guelph, Ontario, N1G 2W1 Canada
| | | | | | | | | | | |
Collapse
|
23
|
Keenleyside WJ, Clarke AJ, Whitfield C. Identification of residues involved in catalytic activity of the inverting glycosyl transferase WbbE from Salmonella enterica serovar borreze. J Bacteriol 2001; 183:77-85. [PMID: 11114903 PMCID: PMC94852 DOI: 10.1128/jb.183.1.77-85.2001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Synthesis of the O:54 O antigen of Salmonella enterica is initiated by the nonprocessive glycosyl transferase WbbE, assigned to family 2 of the glycosyl transferase enzymes (GT2). GT2 enzymes possess a characteristic N-terminal domain, domain A. Based on structural data from the GT2 representative SpsA (S. J. Charnock and G. J. Davies, Biochemistry 38:6380-6385, 1999), this domain is responsible for nucleotide binding. It possesses two invariant Asp residues, the first forming a hydrogen bond to uracil and the second coordinating a Mn(2+) ion. Site-directed replacement of Asp41 (D41A) of WbbE, the analogue of the first Asp residue of SpsA, revealed that this is not required for activity. WbbE possesses three Asp residues near the position analogous to the second conserved residue. Whereas D95A reduced WbbE activity, activity in D93A and D96A mutants was abrogated, suggesting that either D93 or D96 may coordinate the Mn(2+) ion. Our studies also identified a C-terminal region of sequence conservation in 22 GT2 members, including WbbE. SpsA was not among these. This region is characterized by an ED(Y) motif. The Glu and Asp residues of this motif were individually replaced in WbbE. E180D in WbbE had greatly reduced activity, and an E180Q replacement completely abrogated activity; however, D181E had no effect. E180 is predicted to reside on a turn. Combined with the alignment of the motif with potential catalytic residues in the GT2 enzymes ExoM and SpsA, we speculate that E180 is the catalytic residue of WbbE. Sequence and predicted structural divergence in the catalytic region of GT2 members suggests that this is not a homogeneous family.
Collapse
Affiliation(s)
- W J Keenleyside
- Department of Microbiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | | | | |
Collapse
|
24
|
Yethon JA, Vinogradov E, Perry MB, Whitfield C. Mutation of the lipopolysaccharide core glycosyltransferase encoded by waaG destabilizes the outer membrane of Escherichia coli by interfering with core phosphorylation. J Bacteriol 2000; 182:5620-3. [PMID: 10986272 PMCID: PMC111012 DOI: 10.1128/jb.182.19.5620-5623.2000] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2000] [Accepted: 07/17/2000] [Indexed: 11/20/2022] Open
Abstract
In Escherichia coli, phosphoryl substituents in the lipopolysaccharide core region are essential for outer membrane stability. Mutation of the core glucosyltransferase encoded by waaG (formerly rfaG) resulted in lipopolysaccharide truncated immediately after the inner core heptose residues, which serve as the sites for phosphorylation. Surprisingly, mutation of waaG also destabilized the outer membrane. Structural analyses of waaG mutant lipopolysaccharide showed that the cause for this phenotype was a decrease in core phosphorylation, an unexpected side effect of the waaG mutation.
Collapse
Affiliation(s)
- J A Yethon
- Canadian Bacterial Diseases Network and Department of Microbiology, University of Guelph, Guelph, Ontario N1G 2W1
| | | | | | | |
Collapse
|
25
|
Yethon JA, Gunn JS, Ernst RK, Miller SI, Laroche L, Malo D, Whitfield C. Salmonella enterica serovar typhimurium waaP mutants show increased susceptibility to polymyxin and loss of virulence In vivo. Infect Immun 2000; 68:4485-91. [PMID: 10899846 PMCID: PMC98355 DOI: 10.1128/iai.68.8.4485-4491.2000] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Escherichia coli, the waaP (rfaP) gene product was recently shown to be responsible for phosphorylation of the first heptose residue of the lipopolysaccharide (LPS) inner core region. WaaP was also shown to be necessary for the formation of a stable outer membrane. These earlier studies were performed with an avirulent rough strain of E. coli (to facilitate the structural chemistry required to properly define waaP function); therefore, we undertook the creation of a waaP mutant of Salmonella enterica serovar Typhimurium to assess the contribution of WaaP and LPS core phosphorylation to the biology of an intracellular pathogen. The S. enterica waaP mutant described here is the first to be both genetically and structurally characterized, and its creation refutes an earlier claim that waaP mutations in S. enterica must be leaky to maintain viability. The mutant was shown to exhibit characteristics of the deep-rough phenotype, despite its ability to produce a full-length core capped with O antigen. Further, phosphoryl modifications in the LPS core region were shown to be required for resistance to polycationic antimicrobials. The waaP mutant was significantly more sensitive to polymyxin in both wild-type and polymyxin-resistant backgrounds, despite the decreased negative charge of the mutant LPSs. In addition, the waaP mutation was shown to cause a complete loss of virulence in mouse infection models. Taken together, these data indicate that WaaP is a potential target for the development of novel therapeutic agents.
Collapse
Affiliation(s)
- J A Yethon
- Canadian Bacterial Diseases Network, University of Guelph, Guelph, Ontario N1G 2W1
| | | | | | | | | | | | | |
Collapse
|
26
|
Amor K, Heinrichs DE, Frirdich E, Ziebell K, Johnson RP, Whitfield C. Distribution of core oligosaccharide types in lipopolysaccharides from Escherichia coli. Infect Immun 2000; 68:1116-24. [PMID: 10678915 PMCID: PMC97256 DOI: 10.1128/iai.68.3.1116-1124.2000] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/1999] [Accepted: 11/29/1999] [Indexed: 11/20/2022] Open
Abstract
In the lipopolysaccharides of Escherichia coli there are five distinct core oligosaccharide (core OS) structures, designated K-12 and R1 to R4. The objective of this work was to determine the prevalences of these core OS types within the species. Unique sequences in the waa (core OS biosynthesis) gene operon were used to develop a PCR-based system that facilitated unequivocal determination of the core OS types in isolates of E. coli. This system was applied to the 72 isolates in the E. coli ECOR collection, a compilation of isolates that is considered to be broadly representative of the genetic diversity of the species. Fifty (69. 4%) of the ECOR isolates contained the R1 core OS, 8 (11.1%) were representatives of R2, 8 (11.1%) were R3, 2 (2.8%) were R4, and only 4 (5.6%) were K-12. R1 is the only core OS type found in all four major phylogenetic groups (A, B1, B2, and D) in the ECOR collection. Virulent extraintestinal pathogenic E. coli isolates tend to be closely related to group B2 and, to a lesser extent, group D isolates. All of the ECOR representatives from the B2 and D groups had the R1 core OS. In contrast, commensal E. coli isolates are more closely related to group A, which contains isolates representing each of the five core OS structures. R3 was the only core OS type found in 38 verotoxigenic E. coli (VTEC) isolates from humans and cattle belonging to the common enterohemorrhagic E. coli serogroups O157, O111, and O26. Although isolates from other VTEC serogroups showed more core OS diversity, the R3 type (83.1% of all VTEC isolates) was still predominant. When non-VTEC commensal isolates from cattle were analyzed, it was found that most possessed the R1 core OS type.
Collapse
Affiliation(s)
- K Amor
- Department of Microbiology, University of Guelph, Guelph, Ontario N1G 2W1
| | | | | | | | | | | |
Collapse
|
27
|
Allard ST, Giraud MF, Whitfield C, Messner P, Naismith JH. The purification, crystallization and structural elucidation of dTDP-D-glucose 4,6-dehydratase (RmlB), the second enzyme of the dTDP-L-rhamnose synthesis pathway from Salmonella enterica serovar typhimurium. Acta Crystallogr D Biol Crystallogr 2000; 56:222-5. [PMID: 10666612 DOI: 10.1107/s0907444999016200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
dTDP-D-glucose 4,6-dehydratase (RmlB) is the second of four enzymes involved in the dTDP-L-rhamnose pathway and catalyzes the dehydration of dTDP-D-glucose to dTDP-4-keto-6-deoxy-D-glucose. The ultimate product of the pathway, dTDP-L-rhamnose, is the precursor of L-rhamnose, which is a key component of the cell wall of many pathogenic bacteria. RmlB from Salmonella enterica serovar Typhimurium has been overexpressed and purified, and crystals of the enzyme have been grown using the sitting-drop vapour-diffusion technique with lithium sulfate as precipitant. Diffraction data have been obtained to a resolution of 2.8 A on a single frozen RmlB crystal which belongs to space group P2(1), with unit-cell parameters a = 111.85, b = 87.77, c = 145.66 A, beta = 131.53 degrees. The asymmetric unit contains four monomers in the form of two RmlB dimers with a solvent content of 62%. A molecular-replacement solution has been obtained and the model is currently being refined.
Collapse
Affiliation(s)
- S T Allard
- Centre for Biomedical Sciences, North Haugh, The University, St Andrews, Fife KY16 9ST, Scotland
| | | | | | | | | |
Collapse
|
28
|
Drummelsmith J, Whitfield C. Translocation of group 1 capsular polysaccharide to the surface of Escherichia coli requires a multimeric complex in the outer membrane. EMBO J 2000; 19:57-66. [PMID: 10619844 PMCID: PMC1171777 DOI: 10.1093/emboj/19.1.57] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Surface expression of the group 1 K30 capsular polysaccharide of Escherichia coli strain E69 (O9a:K30) requires Wza(K30), a member of the outer membrane auxiliary (OMA) protein family. A mutation in wza(K30) severely restricts the formation of the K30 capsular structure on the cell surface, but does not interfere with the biosynthesis or polymerization of the K30 repeat unit. Here we show that Wza(K30) is a surface-exposed outer membrane lipoprotein. Wza(K30) multimers form ring-like structures in the outer membrane that are reminiscent of the secretins of type II and III protein translocation systems. We propose that Wza(K30) forms an outer membrane pore through which the K30-capsular antigen is translocated. This is the first evidence of a potential mechanism for translocation of high molecular weight polysaccharide across the outer membrane. The broad distribution of the OMA protein family suggests a similar process for polysaccharide export in diverse Gram-negative bacteria.
Collapse
Affiliation(s)
- J Drummelsmith
- Department of Microbiology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | | |
Collapse
|
29
|
Giraud MF, McMiken HJ, Leonard GA, Messner P, Whitfield C, Naismith JH. Overexpression, purification, crystallization and preliminary structural study of dTDP-6-deoxy-L-lyxo-4-hexulose reductase (RmlD), the fourth enzyme of the dTDP-L-rhamnose synthesis pathway, from Salmonella enterica serovar Typhimurium. Acta Crystallogr D Biol Crystallogr 1999; 55:2043-6. [PMID: 10666586 DOI: 10.1107/s0907444999012251] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
L-Rhamnose is an essential component of the cell wall of many pathogenic bacteria. Its precursor, dTDP-L-rhamnose, is synthesized from alpha-D-glucose-1-phosphate and dTTP via a pathway requiring four distinct enzymes: RmlA, RmlB, RmlC and RmlD. RmlD catalyses the terminal step of this pathway by converting dTDP-6-deoxy-L-lyxo-4-hexulose to dTDP-L-rhamnose. RmlD from -Salmonella enterica serovar Typhimurium has been overexpressed in Escherichia coli. The recombinant protein was purified by a two--step protocol involving anion-exchange and hydrophobic chromatography. Dynamic light-scattering experiments indicated that the recombinant protein is monodisperse. Crystals of native and selenomethionine-enriched RmlD have been obtained using the sitting-drop vapour-diffusion method with polyethylene glycol as precipitant. Diffraction data have been collected from orthorhombic crystals of both native and selenomethionyl-derivatized protein, allowing tracing of the protein structure.
Collapse
Affiliation(s)
- M F Giraud
- Centre for Biomolecular Sciences, The University of St Andrews, St Andrews, Fife KY16 9ST, Scotland
| | | | | | | | | | | |
Collapse
|
30
|
Graninger M, Nidetzky B, Heinrichs DE, Whitfield C, Messner P. Characterization of dTDP-4-dehydrorhamnose 3,5-epimerase and dTDP-4-dehydrorhamnose reductase, required for dTDP-L-rhamnose biosynthesis in Salmonella enterica serovar Typhimurium LT2. J Biol Chem 1999; 274:25069-77. [PMID: 10455186 DOI: 10.1074/jbc.274.35.25069] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The thymidine diphosphate-L-rhamnose biosynthesis pathway is required for assembly of surface glycoconjugates in a growing list of bacterial pathogens, making this pathway a potential therapeutic target. However, the terminal reactions have not been characterized. To complete assignment of the reactions, the four enzymes (RmlABCD) that constitute the pathway in Salmonella enterica serovar Typhimurium LT2 were overexpressed. The purified RmlC and D enzymes together catalyze the terminal two steps involving NAD(P)H-dependent formation of dTDP-L-rhamnose from dTDP-6-deoxy-D-xylo-4-hexulose. RmlC was assigned as the thymidine diphosphate-4-dehydrorhamnose 3,5-epimerase by showing its activity to be NAD(P)H-independent. Spectrofluorometric and radiolabeling experiments were used to demonstrate the ability of RmlC to catalyze the formation of dTDP-6-deoxy-L-lyxo-4-hexulose from dTDP-6-deoxy-D-xylo-4-hexulose. Under reaction conditions, RmlC converted approximately 3% of its substrate to product. RmlD was unequivocally identified as the thymidine diphosphate-4-dehydrorhamnose reductase. The reductase property of RmlD was shown by equilibrium analysis and its ability to enable efficient biosynthesis of dTDP-L-rhamnose, even in the presence of low amounts of dTDP-6-deoxy-L-lyxo-4-hexulose. Comparison of 23 known and predicted RmlD sequences identified several conserved amino acid residues, especially the serine-tyrosine-lysine catalytic triad, characteristic for members of the reductase/epimerase/dehydrogenase protein superfamily. In conclusion, RmlD is a novel member of this protein superfamily.
Collapse
Affiliation(s)
- M Graninger
- Zentrum für Ultrastrukturforschung und Ludwig Boltzmann-Institut für Molekulare Nanotechnologie, Universität für Bodenkultur Wien, A-1180 Wien, Austria
| | | | | | | | | |
Collapse
|
31
|
Rahn A, Drummelsmith J, Whitfield C. Conserved organization in the cps gene clusters for expression of Escherichia coli group 1 K antigens: relationship to the colanic acid biosynthesis locus and the cps genes from Klebsiella pneumoniae. J Bacteriol 1999; 181:2307-13. [PMID: 10094716 PMCID: PMC93651 DOI: 10.1128/jb.181.7.2307-2313.1999] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Group 1 capsules of Escherichia coli are similar to the capsules produced by strains of Klebsiella spp. in terms of structure, genetics, and patterns of expression. The striking similarities between the capsules of these organisms prompted a more detailed investigation of the cps loci encoding group 1 capsule synthesis. Six strains of K. pneumoniae and 12 strains of E. coli were examined. PCR analysis showed that the clusters in these strains are conserved in their chromosomal locations. A highly conserved block of four genes, orfX-wza-wzb-wzc, was identified in all of the strains. The wza and wzc genes are required for translocation and surface assembly of E. coli K30 antigen. The conservation of these genes points to a common pathway for capsule translocation. A characteristic JUMPstart sequence was identified upstream of each cluster which may function in conjunction with RfaH to inhibit transcriptional termination at a stem-loop structure found immediately downstream of the "translocation-surface assembly" region of the cluster. Interestingly, the sequence upstream of the cps clusters in five E. coli strains and one Klebsiella strain indicated the presence of IS elements. We propose that the IS elements were responsible for the transfer of the cps locus between organisms and that they may continue to mediate recombination between strains.
Collapse
Affiliation(s)
- A Rahn
- Department of Microbiology, The University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | | | | |
Collapse
|
32
|
Giraud MF, Gordon FM, Whitfield C, Messner P, McMahon SA, Naismith JH. Purification, crystallization and preliminary structural studies of dTDP-6-deoxy-D-xylo-4-hexulose 3,5-epimerase (RmlC), the third enzyme of the dTDP-L-rhamnose synthesis pathway, from Salmonella enterica serovar typhimurium. Acta Crystallogr D Biol Crystallogr 1999; 55:706-8. [PMID: 10089454 DOI: 10.1107/s0907444998015042] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
L-Rhamnose is an essential component of the cell wall of many pathogenic bacteria. Its precusor, dTDP-L-rhamnose, is synthesized from alpha-D-glucose-1-phosphate and dTTP via a pathway requiring four distinct enzymes: RmlA, RmlB, RmlC and RmlD. RmlC was overexpressed in Escherichia coli. The recombinant protein was purified by a two-step protocol involving anion-exchange and hydrophobic chromatography. Dynamic light-scattering experiments indicated that the recombinant protein is monodisperse. Crystals were obtained using the sitting-drop vapour-diffusion method with ammonium sulfate as precipitant. Diffraction data were collected on a frozen crystal to a resolution of 2.17 A. The crystal belongs to either space group P3121 or P3221, with unit-cell parameters a = b = 71.56, c = 183.53 A and alpha = beta = 90, gamma = 120 degrees.
Collapse
Affiliation(s)
- M F Giraud
- Centre for Biomolecular Sciences, Purdie Building, University of St. Andrews, Fife KY16 9ST, Scotland
| | | | | | | | | | | |
Collapse
|
33
|
Abstract
The group 1 K30 antigen from Escherichia coli (O9a:K30) is present on the cell surface as both a capsular structure composed of high-molecular-weight K30 polysaccharide and as short K30 oligosaccharides linked to lipid A-core in a lipopolysaccharide molecule (K30LPS). To determine the molecular processes that are responsible for the two forms of K antigen, the 16 kb chromosomal cps region has been characterized. This region encodes 12 gene products required for the synthesis, polymerization and translocation of the K30 antigen. The gene products include four glycosyltransferases responsible for synthesis of the K30 repeat unit; a PST (1) exporter (Wzx), required to transfer lipid-linked K30 units across the plasma membrane to the periplasmic space; and a K30-antigen polymerase (Wzy). These gene products are typical of those seen in O-antigen biosynthesis gene clusters and they interact with the lipopolysaccharide translocation pathway to express K30LPS on the cell surface. The same gene products also provide the biosynthetic intermediates for the capsule assembly pathway, although they are not in themselves sufficient for synthesis of the K30 capsule. Three additional genes, wza, wzb and wzc, encode homologues to proteins that are encoded by gene clusters involved in expression of a variety of bacterial exopolysaccharides. Mutant analysis indicates that Wza and Wzc are required for wild-type surface expression of the capsular structure but are not essential for polymerization and play no role in the translocation of K30LPS. These surface expression components provide the key feature that distinguishes the assembly systems for O antigens and capsules.
Collapse
Affiliation(s)
- J Drummelsmith
- Department of Microbiology, University of Guelph, Ontario, Canada
| | | |
Collapse
|
34
|
Abstract
Many Escherichia coli strains are covered in a layer of surface-associated polysaccharide called the capsule. Capsular polysaccharides represent a major surface antigen, the K antigen, and more than 80 distinct K serotypes result from structural diversity in these polymers. However, not all capsules consist of K antigen. Some are due to production of an extensive layer of a polymer structurally identical to a lipopolysaccharide O antigen, but distinguished from lipopolysaccharide by the absence of terminal lipid A-core. Recent research has provided insight into the manner in which capsules are organized on the Gram-negative cell surface, the pathways used for their assembly, and the regulatory processes used to control their expression. A limited repertoire of capsule expression systems are available, despite the fact that the producing bacteria occupy a variety of ecological niches and possess diverse physiologies. All of the known capsule assembly systems seen in Gram-negative bacteria are represented in E. coli, as are the majority of the regulatory strategies. Escherichia coli therefore provides a variety of working models on which studies in other bacteria are (or can be) based. In this review, we present an overview of the current molecular and biochemical models for capsule expression in E. coli. By taking into account the organization of capsule gene clusters, details of the assembly pathway, and regulatory features that dictate capsule expression, we provide a new classification system that separates the known capsules of E. coli into four distinct groups.
Collapse
Affiliation(s)
- C Whitfield
- Department of Microbiology, University of Guelph, Ontario, Canada.
| | | |
Collapse
|
35
|
Amor PA, Yethon JA, Monteiro MA, Whitfield C. Assembly of the K40 antigen in Escherichia coli: identification of a novel enzyme responsible for addition of L-serine residues to the glycan backbone and its requirement for K40 polymerization. J Bacteriol 1999; 181:772-80. [PMID: 9922239 PMCID: PMC93442 DOI: 10.1128/jb.181.3.772-780.1999] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli O8:K40 coexpresses two distinct lipopolysaccharide (LPS) structures on its surface. The O8 polysaccharide is a mannose homopolymer with a trisaccharide repeat unit and is synthesized by an ABC-2 transport-dependent pathway. The K40LPS backbone structure is composed of a trisaccharide repeating unit of N-acetylglucosamine (GlcNAc) and glucuronic acid (GlcA) and has an uncommon substitution, an L-serine moiety attached to glucuronic acid. The gene cluster responsible for synthesis of the K40 polysaccharide has previously been cloned and sequenced and was found to contain six open reading frames (ORFs) (P. A. Amor and C. Whitfield, Mol. Microbiol. 26:145-161, 1997). Here, we demonstrate that insertional inactivation of orf1 results in the accumulation of a semirough (SR)-K40LPS form which retains reactivity with specific polyclonal serum in Western immunoblots. Structural and compositional analysis of the SR-K40LPS reveals that it comprises a single K40 repeat unit attached to lipid A core. The lack of polymerization of the K40 polysaccharide indicates that orf1 encodes the K40 polymerase (Wzy) and that assembly of the K40 polysaccharide occurs via a Wzy-dependent pathway (in contrast to that of the O8 polysaccharide). Inactivation of orf3 also results in the accumulation of an SR-LPS form which fails to react with specific polyclonal K40 serum in Western immunoblots. Methylation linkage analysis and fast atom bombardment-mass spectrometry of this SR-LPS reveals that the biological repeat unit of the K40 polysaccharide is GlcNAc-GlcA-GlcNAc. Additionally, this structure lacks the L-serine substitution of GlcA. These results show that (i) orf3 encodes the enzyme responsible for the addition of the L-serine residue to the K40 backbone and (ii) substitution of individual K40 repeats with L-serine is essential for their recognition and polymerization into the K40 polysaccharide by Wzy.
Collapse
Affiliation(s)
- P A Amor
- Department of Microbiology, University of Guelph, Guelph, Ontario N1G 2W1
| | | | | | | |
Collapse
|
36
|
Heinrichs DE, Yethon JA, Amor PA, Whitfield C. The assembly system for the outer core portion of R1- and R4-type lipopolysaccharides of Escherichia coli. The R1 core-specific beta-glucosyltransferase provides a novel attachment site for O-polysaccharides. J Biol Chem 1998; 273:29497-505. [PMID: 9792656 DOI: 10.1074/jbc.273.45.29497] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The major core oligosaccharide biosynthesis operons from prototype Escherichia coli strains displaying R1 and R4 lipopolysaccharide core types were polymerase chain reaction-amplified and analyzed. Comparison of deduced products of the open reading frames between the two regions indicate that all but two share total similarities of 94% or greater. Core oligosaccharide structures resulting from nonpolar insertion mutations in each gene of the core OS biosynthesis operon in the R1 strain allowed assignment of all of the glycosyltransferase enzymes required for outer core assembly. The difference between the R1 and R4 core oligosaccharides results from the specificity of the WaaV protein (a beta1, 3-glucosyltransferase) in R1 and WaaX (a beta1, 4-galactosyltransferase) in R4. Complementation of the waaV mutant of the R1 prototype strain with the waaX gene of the R4 strain converted the core oligosaccharide from an R1- to an R4-type lipopolysaccharide core molecule. Aside from generating core oligosaccharide specificity, the unique beta-linked glucopyranosyl residue of the R1 core plays a crucial role in organization of the lipopolysaccharide. This residue provides a novel attachment site for lipid A-core-linked polysaccharides and distinguishes the R1-type LPS from existing models for enterobacterial lipopolysaccharides.
Collapse
Affiliation(s)
- D E Heinrichs
- Department of Microbiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | | | | | | |
Collapse
|
37
|
Yethon JA, Heinrichs DE, Monteiro MA, Perry MB, Whitfield C. Involvement of waaY, waaQ, and waaP in the modification of Escherichia coli lipopolysaccharide and their role in the formation of a stable outer membrane. J Biol Chem 1998; 273:26310-6. [PMID: 9756860 DOI: 10.1074/jbc.273.41.26310] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The waaY, waaQ, and waaP genes are located in the central operon of the waa (formerly rfa) locus on the chromosome of Escherichia coli. This locus contains genes whose products are involved in the assembly of the core region of the lipopolysaccharide molecule. In the R1 core prototype strain, E. coli F470, there are nine genes in this operon, and all but waaY, waaQ, and waaP have been assigned function. In this study, the waaY, waaQ, and waaP genes were independently mutated by insertion of a non-polar antibiotic resistance cassette, and the structures of the resulting mutant core oligosaccharides were determined by chemical analyses and phosphorus-nuclear magnetic resonance spectroscopy. All three of these mutations were shown to affect the modification of the heptose region of the core, a region whose structure is critical to outer membrane stability. Mutation of waaY resulted in a core oligosaccharide devoid of phosphate on HepII. Mutation of waaQ resulted in loss of the branch HepIII residue on HepII and impeded the activity of WaaY. Mutation of waaP resulted in loss of phosphoryl substituents on HepI and obviated WaaQ and WaaY activity. Only mutation of waaP resulted in hypersensitivity to novobiocin and sodium dodecyl sulfate, a characteristic of deep-rough mutations.
Collapse
Affiliation(s)
- J A Yethon
- Department of Microbiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | | | | | | | | |
Collapse
|
38
|
Heinrichs DE, Yethon JA, Whitfield C. Molecular basis for structural diversity in the core regions of the lipopolysaccharides of Escherichia coli and Salmonella enterica. Mol Microbiol 1998; 30:221-32. [PMID: 9791168 DOI: 10.1046/j.1365-2958.1998.01063.x] [Citation(s) in RCA: 291] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Bacterial lipopolysaccharides (LPS) are unique and complex glycolipids that provide characteristic components of the outer membranes of Gram-negative bacteria. In LPS of the Enterobacteriaceae, the core oligosaccharide links a highly conserved lipid A to the antigenic O-polysaccharide. Structural diversity in the core oligosaccharide is limited by the constraints imposed by its essential role in outer membrane stability and provides a contrast to the hypervariable O-antigen. The genetics of core oligosaccharide biosynthesis in Salmonella and Escherichia coli K-12 have served as prototypes for studies on the LPS and lipo-oligosaccharides from a growing range of bacteria. However, despite the wealth of knowledge, there remains a number of unanswered questions, and direct experimental data are not yet available to define the precise mechanism of action of many gene products. Here we present a comparative analysis of the recently completed sequences of the major core oligosaccharide biosynthesis gene clusters from the five known core types in E. coli and the Ra core type of Salmonella enterica serovar Typhimurium and discuss advances in the understanding of the related biosynthetic pathways. Differences in these clusters reflect important structural variations in the outer core oligosaccharides and provide a basis for ascribing functions to the genes in these model clusters, whereas highly conserved regions within these clusters suggest a critical and unalterable function for the inner region of the core.
Collapse
Affiliation(s)
- D E Heinrichs
- Department of Microbiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | | | | |
Collapse
|
39
|
Heinrichs DE, Monteiro MA, Perry MB, Whitfield C. The assembly system for the lipopolysaccharide R2 core-type of Escherichia coli is a hybrid of those found in Escherichia coli K-12 and Salmonella enterica. Structure and function of the R2 WaaK and WaaL homologs. J Biol Chem 1998; 273:8849-59. [PMID: 9535865 DOI: 10.1074/jbc.273.15.8849] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In Escherichia coli F632, the 14-kilobase pair chromosomal region located between waaC (formerly rfaC) and waaA (kdtA) contains genes encoding enzymes required for the synthesis of the type R2 core oligosaccharide portion of lipopolysaccharide. Ten of the 13 open reading frames encode predicted products sharing greater than 90% total similarity with homologs in E. coli K-12. However, the products of waaK (rfaK) and waaL (rfaL) each resemble homologs in Salmonella enterica serovar Typhimurium but share little similarity with E. coli K-12. The F632 WaaK and WaaL proteins therefore define differences between the type R2 and K-12 outer core oligosaccharides of E. coli lipopolysaccharides. Based on the chemical structure of the core oligosaccharide of an E. coli F632 waaK::aacC1 mutant and in vitro glycosyltransferase analyses, waaK encodes UDP-N-acetylglucosamine:(glucose) lipopolysaccharide alpha1, 2-N-acetylglucosaminyltransferase. The WaaK enzyme adds a terminal GlcNAc side branch substituent that is crucial for the recognition of core oligosaccharide acceptor by the O-polysaccharide ligase, WaaL. Results of complementation analyses of E. coli K-12 and F632 waaL mutants suggest that structural differences between the WaaL proteins play a role in recognition of, and interaction with, terminal lipopolysaccharide core moieties.
Collapse
Affiliation(s)
- D E Heinrichs
- Department of Microbiology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | | | | | | |
Collapse
|
40
|
Amor PA, Whitfield C. Molecular and functional analysis of genes required for expression of group IB K antigens in Escherichia coli: characterization of the his-region containing gene clusters for multiple cell-surface polysaccharides. Mol Microbiol 1997; 26:145-61. [PMID: 9383197 DOI: 10.1046/j.1365-2958.1997.5631930.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Escherichia coli group I capsular K antigens are found in two forms on the cell surface. The K(LPS) form is linked to lipopolysaccharide lipid A core, whereas the high-molecular-weight capsular form is assembled independently of lipid A core. Subgroup IB K antigens are generally co-expressed with either the O8 or O9 antigen and, under the appropriate conditions, with the exopolysaccharide, colanic acid. To examine the relationships between the genetic loci and the synthetic pathways for these various cell-surface polymers, the gene cluster responsible for expression of a prototype group IB K antigen (serotype K40) was cloned and the flanking chromosomal regions characterized. Analysis of the six orfs within the cluster indicates features typical of Wzy (Rfc)-dependent O antigens. Synthesis of group IB K antigens is initiated by WecA (Rfe), a UDP-GlcNAc::undecaprenylphosphate GlcNAc-1-phosphate transferase, and the chain length of K40LPS is determined by the wzz gene product. The his-region of the E. coli O8:K40 prototype is almost exclusively devoted to the expression of three different surface polysaccharides. The rfbK40 cluster is located adjacent to the cps (colanic acid synthesis) and rfbO8 (O8 antigen synthesis) loci in the gene order: his-rfbO8/O9-wzz-ugd-gnd-rfbK40-galF-cps. Thus, rfbK40 is in the location occupied by other Wzy-dependent rfb gene clusters, and rfbO8/O9 represents an additional locus.
Collapse
Affiliation(s)
- P A Amor
- Department of Microbiology, University of Guelph, Ontario, Canada
| | | |
Collapse
|
41
|
Trautmann M, Ruhnke M, Rukavina T, Held TK, Cross AS, Marre R, Whitfield C. O-antigen seroepidemiology of Klebsiella clinical isolates and implications for immunoprophylaxis of Klebsiella infections. Clin Diagn Lab Immunol 1997; 4:550-5. [PMID: 9302204 PMCID: PMC170594 DOI: 10.1128/cdli.4.5.550-555.1997] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
To provide a database for the development of an O-antigen-polysaccharide-containing vaccine against Klebsiella spp., we examined the O-antigen seroepidemiology of 378 Klebsiella clinical isolates collected prospectively in two university centers. Strains were typed by competitive enzyme-linked immunosorbent assay with rabbit antisera specific for serogroups O1 to O12 and monoclonal antibodies (MAbs) specific for serogroups O1, O2ab, O2ac, and the genus-specific core antigen. The numbers of isolates (percentages) of individual O serogroups were as follows: 148 (39.2) for serogroup O1, 40 (10.6) for serogroup O2ab, 4 (1.1) for serogroup O2ac, 89 (23.6) for serogroup O3, 2 (0.5) for serogroup O4, 32 (8.5) for serogroup O5, none for serogroups O7, O9, and O12, and 21 (5.6) for serogroup O11. Forty-two (11.1) of the strains were non-O-typeable. O-serogroup distributions were virtually identical between isolates from invasive infections and those from noninvasive infections or colonizations. A vaccine containing the O-specific polysaccharides of serogroups O1, O2ab, O3, and O5 would cover 82% of clinically occurring O-antigen specificities. Three hundred thirty-eight of 378 isolates (89.4%) reacted with the genus-specific MAb V/9-5, which recognizes an epitope of the outer core region of Klebsiella lipopolysaccharide. Antibodies directed against this epitope may represent a further alternative for O-antigen-targeted immunoprophylaxis of Klebsiella infections. These data support further experimental investigations on the protective potential of O-antigen-based vaccines and/or hyperimmune globulins in Klebsiella infection.
Collapse
Affiliation(s)
- M Trautmann
- Department of Medical Microbiology and Hygiene, University of Ulm, Germany
| | | | | | | | | | | | | |
Collapse
|
42
|
Drummelsmith J, Amor PA, Whitfield C. Polymorphism, duplication, and IS1-mediated rearrangement in the chromosomal his-rfb-gnd region of Escherichia coli strains with group IA and capsular K antigens. J Bacteriol 1997; 179:3232-8. [PMID: 9150218 PMCID: PMC179101 DOI: 10.1128/jb.179.10.3232-3238.1997] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Individual Escherichia coli strains produce several cell surface polysaccharides. In E. coli E69, the his region of the chromosome contains the rfb (serotype O9 lipopolysaccharide O-antigen biosynthesis) and cps (serotype K30 group IA capsular polysaccharide biosynthesis) loci. Polymorphisms in this region of the Escherichia coli chromosome reflect extensive antigenic diversity in the species. Previously, we reported a duplication of the manC-manB genes, encoding enzymes involved in GDP-mannose formation, upstream of rfb in strain E69 (P. Jayaratne et al., J. Bacteriol. 176:3126-3139, 1994). Here we show that one of the manC-manB copies is flanked by IS1 elements, providing a potential mechanism for the gene duplication. Adjacent to manB1 on the IS1-flanked segment is a further open reading frame (ugd), encoding uridine-5'-diphosphoglucose dehydrogenase. The Ugd enzyme is responsible for the production of UDP-glucuronic acid, a precursor required for K30 antigen synthesis. Construction of a chromosomal ugd::Gm(r) insertion mutation demonstrated the essential role for Ugd in the biosynthesis of the K30 antigen and confirmed that there is no additional functional ugd copy in strain E69. PCR amplification and Southern hybridization were used to examine the distribution of IS1 elements and ugd genes in the vicinity of rfb in other E. coli strains, producing different group IA K antigens. The relative order of genes and, where present, IS1 elements was established in these strains. The regions adjacent to rfb in these strains are highly variable in both size and gene order, but in all cases where a ugd homolog was present, it was found near rfb. The presence of IS1 elements in the rfb regions of several of these strains provides a potential mechanism for recombination and deletion events which could contribute to the antigenic diversity seen in surface polysaccharides.
Collapse
Affiliation(s)
- J Drummelsmith
- Department of Microbiology, University of Guelph, Ontario, Canada
| | | | | |
Collapse
|
43
|
Köplin R, Brisson JR, Whitfield C. UDP-galactofuranose precursor required for formation of the lipopolysaccharide O antigen of Klebsiella pneumoniae serotype O1 is synthesized by the product of the rfbDKPO1 gene. J Biol Chem 1997; 272:4121-8. [PMID: 9020123 DOI: 10.1074/jbc.272.7.4121] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The O-side-chain polysaccharide in the lipopolysaccharide of Klebsiella pneumoniae O1 is based on a backbone structure of repeat units of [-->3)-beta-D-Galf-(1-->3)-alpha-D-Galp-(1-->]; this structure is termed D-galactan I. The rfb (O-antigen biosynthesis) gene cluster directs the synthesis of D-galactan I and consists of six genes termed rfbA-FKPO1. In this paper we show that rfbDKPO1 encodes a UDP-galactopyranose mutase (NAD(P)H-requiring) (EC 5.4.99. 9), which forms uridine 5'-(trihydrogen diphosphate) P'-alpha-D-galactofuranosyl ester (UDP-Galf), the biosynthetic precursor of galactofuranosyl residues. The deduced amino acid sequence of rfbDKPO1 shows 85% and 37.5% identity to the rfbDKPO8 gene of K. pneumoniae serotype O8 and the glf gene of Escherichia coli, respectively. The molecular mass of the purified RfbDKPO1 enzyme is 45 kDa as determined by SDS-polyacrylamide gel electrophoresis, while gel filtration revealed a molecular mass of 92 kDa, suggesting a dimeric structure for the native protein. The rfbDKPO1 gene product interconverts uridine 5'-(trihydrogen diphosphate) P'-alpha-D-galactopyranosyl ester (UDP-Galp) and UDP-Galf. Unlike Glf, RfbDKPO1 showed a requirement for NADH or NADPH, which could not be replaced by NAD or NADP. RfbDKPO1 was used to synthesize milligram quantities of UDP-Galf, allowing this compound to be purified and fully characterized in an intact form for the first time. The structure of UDP-Galf was proven by NMR spectroscopy.
Collapse
Affiliation(s)
- R Köplin
- Canadian Bacterial Diseases Network, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | | | | |
Collapse
|
44
|
Whitfield C, Amor PA, Köplin R. Modulation of the surface architecture of gram-negative bacteria by the action of surface polymer:lipid A-core ligase and by determinants of polymer chain length. Mol Microbiol 1997; 23:629-38. [PMID: 9157235 DOI: 10.1046/j.1365-2958.1997.2571614.x] [Citation(s) in RCA: 119] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Lipopolysaccharides (LPSs) are complex glycolipids found in the outer membrane of Gram-negative bacteria. The lipid A-core component of the LPS molecule provides a versatile anchor to which a surface polymer:lipid A-core ligase enzyme can attach one or more structurally distinct surface polymers in a single bacterial strain. In some cases the same polymer can be found on the cell surface in both lipid A-core-linked and -unlinked forms. Analysis by SDS-PAGE of populations of LPS molecules extracted from bacterial cells indicates that there is extensive heterogeneity in their size distribution. Much of the heterogeneity results from complex modal distributions in the chain length of the polymers which are attached to lipid A-core. This is the result of preferential ligation of polymers with specific degrees of polymerization during the assembly of the LPS molecule. The surface architecture of the Gram-negative bacterial cell is therefore profoundly affected by the activities of the surface polymer:lipid A-core ligase and by molecular determinants of polymer chain length. Because of the involvement of cell-surface polymers in interactions between pathogenic bacteria and their hosts, these enzymatic activities also have an important impact on virulence. In this review, the organization of LPSs and related surface polymers will be described and the current understanding of the molecular mechanisms involved in surface diversity will be discussed. Emphasis is placed on the Enterobacteriaceae, but similarities to other bacteria suggest that aspects of the enterobacterial system will have broader significance.
Collapse
Affiliation(s)
- C Whitfield
- Department of Microbiology, University of Guelph, Ontario, Canada.
| | | | | |
Collapse
|
45
|
Reeves PR, Hobbs M, Valvano MA, Skurnik M, Whitfield C, Coplin D, Kido N, Klena J, Maskell D, Raetz CR, Rick PD. Bacterial polysaccharide synthesis and gene nomenclature. Trends Microbiol 1996; 4:495-503. [PMID: 9004408 DOI: 10.1016/s0966-842x(97)82912-5] [Citation(s) in RCA: 398] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Gene nomenclature for bacterial surface polysaccharides is complicated by the large number of structures and genes. We propose a scheme applicable to all species that distinguishes different classes of genes, provides a single name for all genes of a given function and greatly facilitates comparative studies.
Collapse
Affiliation(s)
- P R Reeves
- Dept of Microbiology, University of Sydney, NSW, Australia.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
46
|
Abstract
The plasmid-encoded gene cluster for O:54 O-polysaccharide synthesis in Salmonella enterica serovar Borreze (rfbO:54) contains three genes that direct synthesis of a ManNAc homopolymer with alternating beta1,3 and beta1,4 linkages. In Escherichia coli K-12, RfbAO:54 adds the first ManNAc residue to the Rfe (UDP-GlcpNAc::undecaprenylphosphate GlcpNAc-1-phosphate transferase)- modified lipopolysaccharide core. Hydrophobic cluster analysis of RfbAO:54 indicates this protein belongs to the ExoU family of nonprocessive beta-glycosyltransferases. Two putative catalytic residues and a potential substrate-binding motif were identified in RfbAO:54. Topological analysis of RfbBO:54 predicts four transmembrane domains and a large central cytoplasmic domain. The latter shares homology with a similar domain in the processive beta-glycosyltransferases Cps3S of Streptococcus pneumoniae and HasA of Streptococcus pyogenes. Hydrophobic cluster analysis of RfbBO:54 and Cps3S indicates both possess the structural features characteristic of the HasA family of processive beta-glycosyltransferases. Four potential catalytic residues and a putative substrate-binding motif were identified in RfbBO:54. In Deltarfb E. coli K-12, RfbAO:54 and RfbBO:54 direct synthesis of smooth O:54 lipopolysaccharide, indicating that this O-polysaccharide involves a novel pathway for O-antigen transport. Based on sequence and structural conservation, 15 new ExoU-related and 17 new HasA-related transferases were identified.
Collapse
Affiliation(s)
- W J Keenleyside
- Department of Microbiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
| | | |
Collapse
|
47
|
Kelly RF, Whitfield C. Clonally diverse rfb gene clusters are involved in expression of a family of related D-galactan O antigens in Klebsiella species. J Bacteriol 1996; 178:5205-14. [PMID: 8752339 PMCID: PMC178318 DOI: 10.1128/jb.178.17.5205-5214.1996] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Klebsiella species express a family of structurally related lipopolysaccharide O antigens which share a common backbone known as D-galactan I. Serotype specificity results from modification of D-galactan I by addition of domains of altered structure or by substitution with O-acetyl and/or alpha-D-Galp side groups with various linkages and stoichiometries. In the prototype, Klebsiella serotype O1, the his-linked rfb gene cluster is required for synthesis of D-galactan I, but genes conferring serotype specificity are unlinked. The D-galactan I part of the O polysaccharide is O acetylated in Klebsiella serotype O8. By cloning the rfb region from Klebsiella serotype O8 and analyzing the O polysaccharide synthesized in Escherichia coli K-12 hosts, we show that, like rfbO1, the rfbO8 region directs formation of unmodified D-galactan I. The rfbAB genes encode an ATP-binding cassette transporter required for export of polymeric D-galactan I across the plasma membrane prior to completion of the lipopolysaccharide molecule by ligation of the O polysaccharide to lipid A-core. Complementation experiments show that the rfbAB gene products in serotypes O1 and O8 are functionally equivalent and interchangeable. Hybridization experiments and physical mapping of the rfb regions in related Klebsiella serotypes suggest the existence of shared rfb genes with a common organization. However, despite the functional equivalence of these rfb gene clusters, at least three distinct clonal groups were detected in different Klebsiella species and subspecies, on the basis of Southern hybridization experiments carried out under high-stringency conditions. The clonal groups cannot be predicted by features of the O-antigen structure. To examine the relationships in more detail, the complete nucleotide sequence of the serotype O8 rfb cluster was determined and compared with that of the serotype O1 prototype. The nucleotide sequences for the six rfb genes showed variations in moles percent G+C values and in the values for nucleotide sequence identity, which ranged from 66.9 to 79.7%. The predicted polypeptides ranged from 64.3% identity (78.4% total similarity) to 94.3% identity (98.0% similarity). The results presented here are not consistent with dissemination of the Klebsiella D-galactan I rfb genes through recent lateral transfer events.
Collapse
Affiliation(s)
- R F Kelly
- Department of Microbiology, University of Guelph, Ontario, Canada
| | | |
Collapse
|
48
|
Abstract
This paper estimates the incremental cost-effectiveness of providing antenatal anti-D prophylaxis in varying dose sizes to either primigravidae or all Rh D negative women. It presents a model for calculating the net cost per 1000 'at risk' women based on the costs of anti-D prophylaxis and the future NHS costs avoided. Incremental cost-effectiveness is measured in terms of the net cost per Rh D-alloimmunization and the net cost per Rh HD loss prevented. Programmes for Rh D negative primigravidae are more cost-effective than the same dose protocol extended to all Rh D negative women. The 1 x 1250 iu programme is the most cost-effective option.
Collapse
Affiliation(s)
- S Vick
- Department of Management and Social Sciences, Queen Margaret College, Edinburgh
| | | | | | | | | |
Collapse
|
49
|
Dodgson C, Amor P, Whitfield C. Distribution of the rol gene encoding the regulator of lipopolysaccharide O-chain length in Escherichia coli and its influence on the expression of group I capsular K antigens. J Bacteriol 1996; 178:1895-902. [PMID: 8606162 PMCID: PMC177883 DOI: 10.1128/jb.178.7.1895-1902.1996] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The rol (cld) gene encodes a protein involved in the expression of lipopolysaccharides in some members of the family Enterobacteriaceae. Rol interacts with one or more components of Rfc-dependent O-antigen biosynthetic complexes to regulate the chain length of lipopolysaccharide O antigens. The Rfc-Rol-dependent pathway for O-antigen synthesis is found in strains with heteropolysaccharide O antigens, and, consistent with this association, rol-homologous sequences were detected in chromosomal DNAs from 17 different serotypes with heteropolysaccharide O antigens. Homopolymer O antigens are synthesized by a pathway that does not involve either Rfc or Rol. It was therefore unexpected when a survey of Escherichia coli strains possessing mannose homopolymer O8 and O9 antigens showed that some strains contained rol. All 11 rol-positive strains coexpressed a group IB capsular K antigen with the O8 or O9 antigen. In contrast, 12 rol-negative strains all produced group IA K antigens in addition to the homopolymer O antigen. Previous research from this and other laboratories has shown that portions of the group I K antigens are attached to lipopolysaccharide lipid A-core, in a form that we have designated K(LPS). By constructing a hybrid strain with a deep rough rfa defect, it was shown that the K40 (group IB) K(LPS) antigen exists primarily as long chains. However, a significant amount of K40 antigen was surface expressed in a lipid A-core-independent pathway. The typical chain length distribution of the K40 antigen was altered by introduction of multicopy rol, suggesting that the K40 group IB K antigen is equivalent to a Rol-dependent O antigen. The prototype K30 (group IA) K antigen is expressed as short oligosaccharides (primarily single repeat units) in K(LPS), as well as a high-molecular-weight lipid A-core-independent form. Introduction of multicopy rol into the K30 strain generated a novel modal pattern of K(LPS) with longer polysaccharide chains. Collectively, these results suggested that group IA K(LPS) is also synthesized by a Rol-dependent pathway and that the typically short oligosaccharide K(LPS) results from the absence of Rol activity in these strains.
Collapse
Affiliation(s)
- C Dodgson
- Department of Microbiology, University of Guelph, Guelph, Ontario, Canada
| | | | | |
Collapse
|
50
|
Severn WB, Kelly RF, Richards JC, Whitfield C. Structure of the core oligosaccharide in the serotype O8 lipopolysaccharide from Klebsiella pneumoniae. J Bacteriol 1996; 178:1731-41. [PMID: 8626303 PMCID: PMC177860 DOI: 10.1128/jb.178.6.1731-1741.1996] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Two classes of mutants with O-antigen-deficient lipopolysaccharides were isolated from the serotype O8 reference strain, belonging to Klebsiella pneumoniae subspecies ozaenae. These mutants were selected by resistance to bacteriophage KO1-2, which recognizes and lyses strains with lipopolysaccharide molecules containing the D-galactan II O antigen. Strain RFK-11 contains a defect in O-antigen synthesis and has a complete core, including the attachment site for O antigen. This mutation is complemented by a plasmid carrying the rfb (O-antigen biosynthesis) gene cluster from the related K. pneumoniae serotype O1. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the lipopolysaccharide from strain RFK-9 has a mobility typical of deep-rough lipopolysaccharide. RFK-9 lipopolysaccharide lacks the attachment site for O antigen. Lipopolysaccharides from strains RFK-9 and RFK-11 were isolated, and their structures were determined by methylation analyses, muclear magnetic resonance spectroscopy, and mass spectroscopy. The deduced O8 core oligosaccharide includes the partial core structure reported for the K. pneumoniae subspecies pneumoniae serotype O1 lipopolysaccharide (M. Süsskind, S. Müller-Leonnies, W. Nimmich, H. Brade, and O. Holst, Carbohydr. Res. 269:C1-7, 1995), consistent with the possibility of a conserved core structure within the species. The core oligosaccharide differs from those of the genera Salmonella and Escherichia by the absence of a hexose-containing outer core, the lack of phosphate residues in the inner core, and the presence of galacturonic acid residues.
Collapse
Affiliation(s)
- W B Severn
- Canadian Bacterial Disease Network, Institute of Biological Sciences, Ottawa, Ontario, Canada
| | | | | | | |
Collapse
|