ORCID Profile
0000-0002-4206-2942
Current Organisation
University Of Strathclyde
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Publisher: Wiley
Date: 03-12-2019
DOI: 10.1111/PBI.13294
Publisher: Springer Science and Business Media LLC
Date: 04-2012
DOI: 10.1038/NSMB.2261
Abstract: Bacteria have mechanisms to export proteins for erse purposes, including colonization of hosts and pathogenesis. A small number of archetypal bacterial secretion machines have been found in several groups of bacteria and mediate a fundamentally distinct secretion process. Perhaps erroneously, proteins called 'autotransporters' have long been thought to be one of these protein secretion systems. Mounting evidence suggests that autotransporters might be substrates to be secreted, not an autonomous transporter system. We have discovered a new translocation and assembly module (TAM) that promotes efficient secretion of autotransporters in proteobacteria. Functional analysis of the TAM in Citrobacter rodentium, Salmonella enterica and Escherichia coli showed that it consists of an Omp85-family protein, TamA, in the outer membrane and TamB in the inner membrane of erse bacterial species. The discovery of the TAM provides a new target for the development of therapies to inhibit colonization by bacterial pathogens.
Publisher: Wiley
Date: 18-06-2014
DOI: 10.1111/MMI.12655
Publisher: International Union of Crystallography (IUCr)
Date: 27-08-2014
DOI: 10.1107/S2053230X14017403
Abstract: TamB is a recently described inner membrane protein that, together with its partner protein TamA, is required for the efficient secretion of a subset of autotransporter proteins in Gram-negative bacteria. In this study, the C-terminal DUF490 963–1138 domain of TamB was overexpressed in Escherichia coli K-12, purified and crystallized using the sitting-drop vapour-diffusion method. The crystals belonged to the primitive trigonal space group P 3 1 21, with unit-cell parameters a = b = 57.34, c = 220.74 Å, and diffracted to 2.1 Å resolution. Preliminary secondary-structure and X-ray diffraction analyses are reported. Two molecules are predicted to be present in the asymmetric unit. Experimental phasing using selenomethionine-labelled protein will be undertaken in the future.
Publisher: Portland Press Ltd.
Date: 21-11-2012
DOI: 10.1042/BST20120206
Abstract: Gram-negative phytopathogens cause significant losses in a erse range of economically important crop plants. The effectiveness of traditional countermeasures, such as the breeding and introduction of resistant cultivars, is often limited by the dearth of available sources of genetic resistance. An alternative strategy to reduce loss to specific bacterial phytopathogens is to use narrow-spectrum protein antibiotics such as colicin-like bacteriocins as biocontrol agents. A number of colicin-like bacteriocins active against phytopathogenic bacteria have been described previously as have strategies for their application to biocontrol. In the present paper, we discuss these strategies and our own recent work on the identification and characterization of candidate bacteriocins and how these potent and selective antimicrobial agents can be effectively applied to the control of economically important plant disease.
Publisher: Oxford University Press (OUP)
Date: 19-10-2012
Abstract: Multicellular organisms limit the availability of free iron to prevent the utilization of this essential nutrient by microbial pathogens. As such, bacterial pathogens possess a variety of mechanisms for obtaining iron from their hosts, including a number of ex les of vertebrate pathogens that obtain iron directly from host proteins. Recently, two novel members of the colicin M bacteriocin family were discovered in Pectobacterium that suggest that this phytopathogen possesses such a system. These bacteriocins (pectocin M1 and M2) consist of a cytotoxic domain homologous to that of colicin M fused to a horizontally acquired plant-like ferredoxin. This ferredoxin domain substitutes the portion of colicin M required for receptor binding and translocation, presumably fulfilling this role by parasitizing an existing ferredoxin-based iron acquisition pathway. The ability of susceptible strains of Pectobacterium to utilize plant ferredoxin as an iron source was also demonstrated, providing additional evidence for the existence of such a system. If this hypothesis is correct, it represents the first ex le of iron piracy directly from a host protein by a phytopathogen and serves as a testament of the flexibility of evolution in creating new bacteriocin specificities.
Publisher: Springer Science and Business Media LLC
Date: 31-10-2016
DOI: 10.1038/NCOMMS13308
Abstract: Iron is a limiting nutrient in bacterial infection putting it at the centre of an evolutionary arms race between host and pathogen. Gram-negative bacteria utilize TonB-dependent outer membrane receptors to obtain iron during infection. These receptors acquire iron either in concert with soluble iron-scavenging siderophores or through direct interaction and extraction from host proteins. Characterization of these receptors provides invaluable insight into pathogenesis. However, only a subset of virulence-related TonB-dependent receptors have been currently described. Here we report the discovery of FusA, a new class of TonB-dependent receptor, which is utilized by phytopathogenic Pectobacterium spp. to obtain iron from plant ferredoxin. Through the crystal structure of FusA we show that binding of ferredoxin occurs through specialized extracellular loops that form extensive interactions with ferredoxin. The function of FusA and the presence of homologues in clinically important pathogens suggests that small iron-containing proteins represent an iron source for bacterial pathogens.
Publisher: Public Library of Science (PLoS)
Date: 09-03-2012
Publisher: International Union of Crystallography (IUCr)
Date: 30-06-2015
DOI: 10.1107/S1399004715008548
Abstract: Bacterial α-2-macroglobulins have been suggested to function in defence as broad-spectrum inhibitors of host proteases that breach the outer membrane. Here, the X-ray structure of protease-cleaved Escherichia coli α-2-macroglobulin is described, which reveals a putative mechanism of activation and conformational change essential for protease inhibition. In this competitive mechanism, protease cleavage of the bait-region domain results in the untethering of an intrinsically disordered region of this domain which disrupts native interdomain interactions that maintain E. coli α-2-macroglobulin in the inactivated form. The resulting global conformational change results in entrapment of the protease and activation of the thioester bond that covalently links to the attacking protease. Owing to the similarity in structure and domain architecture of Escherichia coli α-2-macroglobulin and human α-2-macroglobulin, this protease-activation mechanism is likely to operate across the erse members of this group.
Publisher: Portland Press Ltd.
Date: 28-07-2016
DOI: 10.1042/BCJ20160470
Abstract: Increasing rates of antibiotic resistance among Gram-negative pathogens such as Pseudomonas aeruginosa means alternative approaches to antibiotic development are urgently required. Pyocins, produced by P. aeruginosa for intraspecies competition, are highly potent protein antibiotics known to actively translocate across the outer membrane of P. aeruginosa. Understanding and exploiting the mechanisms by which pyocins target, penetrate and kill P. aeruginosa is a promising approach to antibiotic development. In this work we show the therapeutic potential of a newly identified tRNase pyocin, pyocin SD2, by demonstrating its activity in vivo in a murine model of P. aeruginosa lung infection. In addition, we propose a mechanism of cell targeting and translocation for pyocin SD2 across the P. aeruginosa outer membrane. Pyocin SD2 is concentrated at the cell surface, via binding to the common polysaccharide antigen (CPA) of P. aeruginosa lipopolysaccharide (LPS), from where it can efficiently locate its outer membrane receptor FpvAI. This strategy of utilizing both the CPA and a protein receptor for cell targeting is common among pyocins as we show that pyocins S2, S5 and SD3 also bind to the CPA. Additional data indicate a key role for an unstructured N-terminal region of pyocin SD2 in the subsequent translocation of the pyocin into the cell. These results greatly improve our understanding of how pyocins target and translocate across the outer membrane of P. aeruginosa. This knowledge could be useful for the development of novel anti-pseudomonal therapeutics and will also support the development of pyocin SD2 as a therapeutic in its own right.
Publisher: Elsevier BV
Date: 08-2015
Publisher: Elsevier BV
Date: 11-2012
Publisher: Public Library of Science (PLoS)
Date: 04-01-2016
Publisher: Elsevier BV
Date: 12-2017
Publisher: Public Library of Science (PLoS)
Date: 06-02-2014
Publisher: Public Library of Science (PLoS)
Date: 04-07-2013
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Daniel Walker.