Crystallographic Study Of The Phosphoethanolamine Transferase EptC required For Polymyxin Resistance And Motility In Campylobacter jejuni

The foodborne enteric pathogen Campylobacter jejuni decorates a variety of its cell-surface structures with phosphoethanolamine (pEtN). Modifying lipid A with pEtN promotes cationic antimicrobial peptide resistance, whereas post-translationally modifying the flagellar rod protein FlgG with pEtN promotes flagellar assembly and motility, which are processes that are important for intestinal colonization. EptC, the pEtN transferase required for all known pEtN cell-surface modifications in C. jejuni, is a predicted inner-membrane metalloenzyme with a five-helix N-terminal transmembrane domain followed by a soluble sulfatase-like catalytic domain in the periplasm. The atomic structure of the catalytic domain of EptC (cEptC) was crystallized and solved to a resolution of 2.40 angstrom. cEptC adopts the alpha/beta/alpha fold of the sulfatase protein family and harbors a zinc-binding site. A phosphorylated Thr266 residue was observed that was hypothesized to mimic a covalent pEtN-enzyme intermediate. The requirement for Thr266 as well as the nearby residues Asn308, Ser309, His358 and His440 was ascertained via in vivo activity assays on mutant strains. The results establish a basis for the design of pEtN transferase inhibitors.National Institutes of Health (grants AI064184, AI076322, GM106112Army Research Office (grantW911NF-12-1-0390)College of Natural SciencesOffice of the Executive Vice President and ProvostInstitute for Cellular and Molecular Biology at the University of Texas at AustinUS DOE DE-AC02-06CH11357National Institute of General Medical SciencesHoward Hughes Medical InstituteOffice of Science, Office of Basic Energy Sciences of the US Department of Energy DE-AC02-05CH11231Maria Person and the Proteomics Facility at the University of Texas at Austin ES007784 (CRED) and RP110782 (CPRIT)Molecular Bioscience

Top-Down Strategies for the Structural Elucidation of Intact Gram-Negative Bacterial Endotoxins

Re-modelling of lipopolysaccharides, which are the primary constituent of the outer cell membrane of Gram-negative bacteria, modulates pathogenesis and resistance to microbials. Reported herein is the characterization of intact Gram-negative bacterial lipooligosaccharides (LOS) via a new strategy utilizing online liquid chromatography (LC) coupled with ultraviolet photodissociation (UVPD) mass spectrometry. Compared to collision-based MS/MS methods, UVPD and UVPD/HCD promoted a greater array of cleavages within both the glycan and lipid moieties, including C-C, C-N, C-O cleavages in the acyl chains as well as glycosidic and cross-ring cleavages, thus providing the most far-reaching structural characterization of LOS. This LC-MS/MS strategy affords a robust analytical method to structurally characterize complex mixtures of bacterial endotoxins that maintains the integrity of the core oligosaccharide and lipid A domains of LOS, providing direct feedback about the cell envelope architectures and LOS modification strategies involved in resistance of the host innate immune defense.NIH R01 GM103655, AI064184, AI76322Army Research Office W911NF-12-1-0390Cystic Fibrosis Foundation TRENT13G0Welch Foundation F-1155Chemistr

Peer-Led Team Learning at the University of West Georgia

Peer-Led Team Learning (PLTL) has been a part of general chemistry at the University of West Georgia (UWG) for over fifteen years. PLTL is a collaborative and innovative learning model that supplements the classroom lecture, typically in STEM courses. In PLTL at UWG, approximately fifteen students meet weekly for ninety minutes to actively work together to solve chemistry problems under the guidance of a peer leader. Results at UWG have shown that students who consistently attend and participate in PLTL attain higher grades and better student learning outcomes such as student engagement, motivation and performance than students who fail to attend. At this session we will model a sample workshop and actively involve participants