Biology subjects

Hoskisson, P. A.

Publications and source records attributed to Hoskisson, P. A..

26 records · Page 2Linked to original sources

bioRxiv2019

A two-lane mechanism for selective biological ammonium transport

The transport of charged molecules across biological membranes faces the dual problem of accommodating charges in a highly hydrophobic environment while maintaining selective substrate translocation. A particular controversy has existed around the mechanism of ammonium exchange by the ubiquitous Amt/Mep/Rh transporter family, an essential process in all kingdoms of life. Here, using a combination of electrophysiology, yeast functional complementation and extended molecular dynamics simulations, we reveal a unique two-lane pathway for electrogenic NH4+ transport in two archetypal members of the family. The pathway underpins a mechanism by which charged H+ and neutral NH3 are carried separately across the membrane after NH4+ deprotonation. This mechanism defines a new principle of achieving transport selectivity against competing ions in a biological transport process.

biochemistry↗

bioRxiv2019

Three-dimensional observations of an aperiodic oscillatory gliding motility behaviour in Myxococcus xanthus using confocal interference reflection microscopy

The Delta-proteobacterium, Myxococcus xanthus, has been used as a model for bacterial motility and to provide insights of bacterial swarming behaviours. Fluorescence microscopy techniques have shown that various mechanisms are involved in gliding motility, but these have almost entirely been limited to 2D studies and there is currently no understanding of gliding motility in a 3D context. We present here the first use of confocal interference reflection microscopy (IRM) to study gliding bacteria, and we reveal aperiodic oscillatory behaviour with changes in the position of the basal membrane relative to the coverglass on the order of 90 nm in vitro. Firstly, we use a model plano-convex lens specimen to show how topological information can be obtained from the wavelength-dependent interference pattern in IRM. We then use IRM to observe gliding M. xanthus and show that cells undergo previously unobserved changes in their height as they glide. We compare the wild-type with mutants of reduced motility, which also exhibit the same changes in adhesion profile during gliding. We find that the general gliding behaviour is independent of the proton motive force-generating complex, AglRQS, and suggest that the novel behaviour we present here may be a result of recoil and force transmission along the length of the cell body following firing of the Type IV pili.

microbiology↗

bioRxiv2019

Parasitic worm product ES-62 promotes healthspan and lifespan in a mouse model of obesity-induced ageing

The recent extension of human lifespan has not been matched by equivalent improvements in late-life health due to the global pandemic in type-2 diabetes, obesity and cardiovascular disease, ageing-associated conditions exacerbated by widespread adoption of the high calorie Western diet (HCD). As a novel therapeutic strategy, we have investigated the potential of ES-62, an immunomodulator secreted by the parasitic worm Acanthocheilonema viteae, to improve healthspan by targeting the chronic inflammation that drives metabolic dysregulation underpinning ageing-induced ill-health. We found that ES-62 improves a range of inflammatory but also pathophysiological, metabolic and microbiome parameters, when administered subcutaneously at only 1 {micro}g/week throughout the lifespan of HCD-fed mice. Strikingly, ES-62 induced sex-specific healthspan signatures and indeed, it substantially increased the median survival of male, but not female, HCD-mice. Modelling of 113 responses contributing to these differential signatures by machine learning approaches now signposts candidate parameters key to promoting both healthspan and lifespan.

immunology↗

bioRxiv2018

Reconciling DNA replication and transcription in a hyphal organism: Spatial dynamics of transcription complexes in live Streptomyces coelicolor A3(2)

Reconciling transcription and DNA replication in the growing hyphae of the filamentous bacterium Streptomyces presents several physical constraints on growth due to their apically extending and branching, multigenomic cells and chromosome replication being independent of cell division. Using a GFP translational fusion to the {beta}-subunit of RNA polymerase (rpoC-egfp), in its native chromosomal location, we observed growing Streptomyces hyphae using time-lapse microscopy throughout the lifecycle and under different growth conditions. The RpoC-eGFP fusion co-localised with DNA around 1.8 m behind the extending tip, whereas replisomes localise around 4-5 m behind the tip, indicating that at the growing tip, transcription and chromosome replication are to some degree spatially separated. Dual-labeled RpoC-egfp/DnaN-mCherry strains also indicate that there is limited co-localisation of transcription and chromosome replication at the extending hyphal tip. This likely facilitates the use of the same DNA molecule for active transcription and chromosome replication in growing cells, independent of cell division. This represents a novel, but hitherto unknown mechanism for reconciling two fundamental processes that utilise the same macromolecular template that allows for rapid growth without compromising chromosome replication in filamentous bacteria and may have implications for evolution of filamentous growth in microorganisms, where uncoupling of DNA replication from cell division is required.

microbiology↗

bioRxiv2018

The parasitic worm product ES-62 normalises the gut microbiota/bone marrow axis in inflammatory arthritis

The human immune system has evolved in the context of our colonisation by bacteria, viruses, fungi and parasitic helminths. Reflecting this, the rapid eradication of pathogens appears to have resulted in reduced microbiome diversity and generation of chronically activated immune systems, presaging the recent rise of allergic, autoimmune and metabolic disorders. Certainly, gastrointestinal helminths can protect against gut and lung mucosa inflammatory conditions by modulating the microbiome and suppressing the chronic inflammation associated with dysbiosis. Here, we employ ES-62, an immunomodulator secreted by tissue-dwelling Acanthocheilonema viteae to show that modulation of the gut microbiome does not require live infection with gastrointestinal-based helminths nor is protection restricted to mucosal diseases. Specifically, subcutaneous administration of this defined parasitic worm product affords protection against joint disease in collagen-induced arthritis, a mouse model of rheumatoid arthritis, which is associated with normalisation of gut microbiota and prevention of loss of intestinal barrier integrity.

immunology↗

bioRxiv2018

Merging in-solution X-ray and neutron scattering data allows fine structural analysis of membrane-protein detergent complexes

AbstractIn-solution small angle X-ray and neutron scattering (SAXS/SANS) have become popular methods to characterize the structure of membrane proteins, solubilized by either detergents or nanodiscs. SANS studies of protein-detergent complexes usually require deuterium-labelled proteins or detergents, which in turn often lead to problems in their expression or purification. Here, we report an approach whose novelty is the combined analysis of SAXS and SANS data from an unlabeled membrane protein complex in solution in two complementary ways. Firstly, an explicit atomic analysis, including both protein and detergent molecules, using the program WAXSiS which has been adapted to predict SANS data. Secondly, the use of MONSA which allows to discriminate between detergent head- and tail-groups in an ab initio approach. Our approach is readily applicable to any detergent-solubilized protein and provides more detailed structural information on protein-detergent complexes from unlabeled samples than SAXS or SANS alone.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=196 SRC=\"FIGDIR/small/324103_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (67K):\norg.highwire.dtl.DTLVardef@f7e17corg.highwire.dtl.DTLVardef@1f4987dorg.highwire.dtl.DTLVardef@1475c79org.highwire.dtl.DTLVardef@839b9_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2018

The lipid environment determines the activity of the E. coli ammonium transporter, AmtB

The movement of ammonium across biological membranes is a fundamental process in all living organisms and is mediated by the ubiquitous Amt/Mep/Rh family of transporters. Recent structural analysis and coupled mass spectrometry studies have shown that the Escherichia coli ammonium transporter, AmtB, specifically binds phosphatidylglycerol (PG). Upon PG binding, several residues of AmtB undergo a small conformational change, which stabilizes the protein against unfolding. However, no studies have so far been conducted to explore if PG binding to AmtB has functional consequences. Here, we used an in vitro experimental assay with purified components together with molecular dynamics simulations to characterise the relation between PG binding and AmtB activity. Firstly, our results indicate that the function of Amt in archaebacteria and eubacteria may differ. Secondly, we show that PG is an essential cofactor for AmtB activity and that in the absence of PG AmtB cannot complete the full translocation cycle. Furthermore, our simulations reveal previously undiscovered PG binding sites on the intracellular side of the lipid bilayer between the AmtB subunits. The possible molecular mechanisms explaining the functional role of PG are discussed.

biochemistry↗

bioRxiv2016

MtrA is an essential regulator that coordinates antibiotic production and development in Streptomyces species

Streptomyces bacteria make numerous secondary metabolites, including half of all known antibiotics. Understanding the global regulation of secondary metabolism is important because most Streptomyces natural products are not made under laboratory conditions and unlocking cryptic biosynthetic gene clusters (BGCs) is a major focus for natural product discovery. Production is coordinated with sporulation but the regulators that coordinate development with antibiotic biosynthesis are largely unknown. Here we characterise a highly conserved actinobacterial response regulator called MtrA in antibiotic-producing Streptomyces species. We show that MtrA is an essential global regulator of secondary metabolism that directly activates antibiotic production in in S. coelicolor and S. venezuelae. MtrA also controls key developmental genes required for DNA replication and cell division and we propose that MtrA is the missing link that coordinates secondary metabolism with development in Streptomyces species.

microbiology↗