Publications by authors named "Helen Ridley"

Objective: To explore the association between baseline pain duration and the likelihood of re-referral of patients with low back pain (LBP) managed on the evidence-based North East of England Regional Back Pain and Radicular Pain Pathway (NERBPP).

Study Design: Longitudinal, observational cohort study.

Methods: In all, 12,509 adults with LBP were identified as having been discharged from the pathway, between May 2015 and December 2019.

View Article and Find Full Text PDF

Study Design: Nonrandomized longitudinal observational study.

Objective: The aim of this study was to evaluate the association between baseline pain duration and medium-to-long term clinical outcomes, in low back pain (LBP) patients enrolled on the North East of England Regional Back Pain and Radicular Pain Pathway (NERBPP).

Summary Of Background Data: The NERBPP is based upon National Institute for Health and Care Excellence (NICE) guidelines.

View Article and Find Full Text PDF

The outer membrane (OM) of gram-negative bacteria is an unusual asymmetric bilayer with an external monolayer of lipopolysaccharide (LPS) and an inner layer of phospholipids. The LPS layer is rigid and stabilized by divalent cation cross-links between phosphate groups on the core oligosaccharide regions. This means that the OM is robust and highly impermeable to toxins and antibiotics.

View Article and Find Full Text PDF

Most colicins kill Escherichia coli cells by membrane pore formation or nuclease activity and, superficially, the mechanisms are similar: receptor binding, translocon recruitment, periplasmic receptor binding and membrane insertion. However, in detail, they employ a wide variety of molecular interactions that reveal a high degree of evolutionary diversification. Group A colicins bind to members of the TolQRAB complex in the periplasm and heterotrimeric complexes of colicin-TolA-TolB have been observed for both ColA and ColE9.

View Article and Find Full Text PDF

Colicins are a diverse family of large antibacterial protein toxins, secreted by and active against Escherichia coli and must cross their target cell's outer membrane barrier to kill. To achieve this, most colicins require an abundant porin (e.g.

View Article and Find Full Text PDF

Bacteria often produce toxins which kill competing bacteria. Colicins, produced by and toxic to Escherichia coli bacteria are three-domain proteins so efficient that one molecule can kill a cell. The C-terminal domain carries the lethal activity and the central domain is required for surface receptor binding.

View Article and Find Full Text PDF

Proteins that translocate across cell membranes need to overcome a significant hydrophobic barrier. This is usually accomplished via specialized protein complexes, which provide a polar transmembrane pore. Exceptions to this include bacterial toxins, which insert into and cross the lipid bilayer itself.

View Article and Find Full Text PDF

Escherichia coli outer membrane protein C (osmoporin) is a close homologue of OmpF or matrix porin, expressed under conditions of high osmolarity or ionic strength. Despite the fact that the proteins display very similar structures (rmsd = 0.78 Å), the channel activities (gating or selectivity) of the two proteins are markedly different, and compared to OmpF, there is much less published information about the stability and folding of OmpC.

View Article and Find Full Text PDF

Colicins are water soluble toxins secreted by E. coli cells to kill other E. coli and related species.

View Article and Find Full Text PDF

Colicin N is a pore-forming bacteriocin that enters target Escherichia coli cells with the assistance of TolA, a protein in the periplasm of the target cell. The N-terminal domain of the colicin that carries the TolA-binding epitope, the translocation domain (T-domain), is intrinsically disordered. From (1)H-(13)C-(15)N NMR studies of isotopically labeled T-domain interacting with unlabeled TolAIII (the C-terminal domain of TolA), we have identified the TolA-binding epitope and have shown that the extent of its disorder is reduced on binding TolA, although it does not fold into a globular structure with defined secondary structure elements.

View Article and Find Full Text PDF

The intrinsically disordered translocation domain (T-domain) of the protein antibiotic colicin N binds to periplasmic receptors of target Escherichia coli cells in order to penetrate their inner membranes. We report here that the specific 27 consecutive residues of the T-domain of colicin N known to bind to the helper protein TolA in target cells also interacts intramolecularly with folded regions of colicin N. We suggest that this specific self-recognition helps intrinsically disordered domains to bury their hydrophobic recognition motifs and protect them against degradation, showing that an impaired self-recognition leads to increased protease susceptibility.

View Article and Find Full Text PDF

A method is presented to produce large amounts of Bcl-2 and Bcl-x(L), two anti-apoptotic proteins of considerable biomedical interest. Expression constructs were prepared in which the Escherichia coli protein TolAIII, known to promote over expression of soluble product, was added to the N-terminus of Bcl-2 or Bcl-x(L) proteins, which had their C-terminal hydrophobic anchors deleted. Here the expression of these TolAIII-fusion constructs, followed by a two-step metal-affinity based purification protocol is described.

View Article and Find Full Text PDF

Colicins kill Escherichia coli after translocation across the outer membrane. Colicin N displays an unusually simple translocation pathway, using the outer membrane protein F (OmpF) as both receptor and translocator. Studies of this binary complex may therefore reveal a significant component of the translocation pathway.

View Article and Find Full Text PDF

Protective antigen (PA) is an 83kDa protein which, although essential for toxicity of Bacillus anthracis, is harmless and an effective vaccine component. In vivo it undergoes receptor binding, proteolysis, heptamerisation and membrane insertion. Here we probe the response of PA to denaturants, temperature and pH.

View Article and Find Full Text PDF

Controlled cell death is fundamental to tissue hemostasis and apoptosis malfunctions can lead to a wide range of diseases. Bcl-x(L) is an anti-apoptotic protein the function of which is linked to its reversible interaction with mitochondrial outer membranes. Its interfacial and intermittent bilayer association makes prediction of its bound structure difficult without using methods able to extract data from dynamic systems.

View Article and Find Full Text PDF

The membrane-bound selenate reductase of Enterobacter cloacae SLD1a-1 is purified in low yield and has relatively low activity in the pure form compared to that of other oxyanion reductases, such as the membrane-bound and periplasmic nitrate reductases. A microtiter plate assay based on the original quartz cuvette viologen assay of Jones and Garland (R.W.

View Article and Find Full Text PDF

Enterobacter cloacae SLD1a-1 is capable of reductive detoxification of selenate to elemental selenium under aerobic growth conditions. The initial reductive step is the two-electron reduction of selenate to selenite and is catalyzed by a molybdenum-dependent enzyme demonstrated previously to be located in the cytoplasmic membrane, with its active site facing the periplasmic compartment (C. A.

View Article and Find Full Text PDF

Enterobacter cloacae SLD1a-1 is capable of reducing selenium oxyanions to elemental selenium under both aerobic and anaerobic conditions. In this study the enzyme that catalyses the initial reduction of selenate (SeO4(2-)) to selenite (SeO3(2-)) has been localised to isolated cytoplasmic membrane fractions. Experiments with intact cells have shown that the putative selenate reductase can accept electrons more readily from membrane-impermeable methyl viologen than membrane-permeable benzyl viologen, suggesting that the location of the catalytic site is towards the periplasmic side of the cytoplasmic membrane.

View Article and Find Full Text PDF