Biology subjects

Hoskisson, P. A.

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

3 recordsLinked to original sources

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↗