Structures of lipopolysaccharides from Klebsiella pneumoniae. Eluicidation of the structure of the linkage region between core and polysaccharide O chain and identification of the residues at the non-reducing termini of the O chains

Deamination of LPSs from Klebsiella pneumoniae released O-chain polysaccharides together with a fragment of the core oligosaccharide. The structures of the products from serotypes O1, O2a, O2a,c, O3, O4, O5, and O12 were determined by NMR spectroscopy and chemical methods, identifying the linkage region between the O antigens and the core as well as novel residues at the non-reducing ends of the polysaccharides. All serotypes had an identical linkage between the O chain and core.     

Biosynthesis of a novel 3-deoxy-D-manno-oct-2-ulosonic acid-containing outer core oligosaccharide in the lipopolysaccharide of Klebsiella pneumoniae

The core oligosaccharide region of Klebsiella pneumoniae lipopolysaccharide contains some novel features that distinguish it from the corresponding lipopolysaccharide region in other members of the Enterobacteriaceae family, such as Escherichia coli and Salmonella. The conserved Klebsiella outer core contains the unusual trisaccharide 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo)-(2,6)-GlcN-(1,4)-GalUA. In general, Kdo residues are normally found in the inner core, but in K. pneumoniae, this Kdo residue provides the ligation site for O polysaccharide. The outer core Kdo residue can also be non-stoichiometrically substituted with an l-glycero-d-manno-heptopyranose (Hep) residue, another component more frequently found in the inner core. To understand the genetics and biosynthesis of core oligosaccharide synthesis in Klebsiella, the gene products involved in the addition of the outer core GlcN (WabH), Kdo (WabI), and Hep (WabJ) residues as well as the inner core HepIII residue (WaaQ) were identified. Non-polar mutations were created in each of the genes, and the resulting mutant lipopolysaccharide was analyzed by mass spectrometry. The in vitro glycosyltransferase activity of WabI and WabH was verified. WabI transferred a Kdo residue from CMP-Kdo onto the acceptor lipopolysaccharide. The activated precursor required for GlcN addition has not been identified. However, lysates overexpressing WabH were able to transfer a GlcNAc residue from UDP-GlcNAc onto the acceptor GalUA residue in the outer core.     

Proteomic Markers and Early Prediction of Alzheimer’s Disease

Biochemistry (Moscow) - Alzheimer’s disease (AD) is the most common socially significant neurodegenerative pathology, which currently affects more than 30 million elderly people worldwide....     

Recreational boating: a large unregulated vector transporting marine invasive species

Aim Recreational boating is arguably the largest unregulated vector for the introduction and spread of marine invasive species. Hull fouling communities have been recognized to harbour non‐indigenous species (NIS), but presence should not be equated with transport. In this study, we characterize the presence of NIS in hull fouling communities, determine if host vessels transport these species and evaluate the importance of recreational boating as a vector for introduction and spread. Location Coastal British Columbia (BC), Canada. Methods Dive surveys in BC marinas were conducted to record the presence of NIS and to estimate their per cent cover. In addition, a boater questionnaire survey was used to determine common travel and maintenance practices. These results were combined to investigate the potential for recreational boats to transport NIS. Results Nine NIS, including the highly invasive ascidians Styela clava and Botrylloides violaceus, and the macroalga Sargassum muticum, were found in hull fouling communities on recreational boats. Overall, per cent cover was generally low; however, niche areas were commonly fouled, even on active and otherwise clean boats. Fouling of niche areas was not related to either antifouling paint age or travel frequency, and fouling levels were highly variable among individual boats both within marinas and across regions. Main conclusions Recreational boating is a major vector contributing to the spread of marine invasive species. Our results indicate that recreational boats represent a high‐risk vector both for primary introduction and secondary spread of marine NIS and should be subject to vector management regulations.     

The redistribution of power: neurocardiac signaling, alcohol and gender

Human adaptability involves interconnected biological and psychological control processes that determine how successful we are in meeting internal and environmental challenges. Heart rate variability (HRV), the variability in consecutive R-wave to R-wave intervals (RRI) of the electrocardiogram, captures synergy between the brain and cardiovascular control systems that modulate adaptive responding. Here we introduce a qualitatively new dimension of adaptive change in HRV quantified as a redistribution of spectral power by applying the Wasserstein distance with exponent 1 metric (W(1)) to RRI spectral data. We further derived a new index, D, to specify the direction of spectral redistribution and clarify physiological interpretation. We examined gender differences in real time RRI spectral power response to alcohol, placebo and visual cue challenges. Adaptive changes were observed as changes in power of the various spectral frequency bands (i.e., standard frequency domain HRV indices) and, during both placebo and alcohol intoxication challenges, as changes in the structure (shape) of the RRI spectrum, with a redistribution towards lower frequency oscillations. The overall conclusions from the present study are that the RRI spectrum is capable of a fluid and highly flexible response, even when oscillations (and thus activity at the sinoatrial node) are pharmacologically suppressed, and that low frequency oscillations serve a crucial but less studied role in physical and mental health.     

Identification of a novel recognition sequence for fibronectin within the NH2-terminal beta-sandwich domain of tissue transglutaminase

Tissue transglutaminase belongs to the multigene transglutaminase family of Ca2+-dependent protein cross-linking enzymes. Unlike other transglutaminases, it is involved in cell-matrix interactions and serves as an adhesion co-receptor for fibronectin. Previous work established that the fibronectin-binding motif(s) is located within the NH2-terminal proteolytic fragment of the protein consisting of residues 1-272. Here we identify a novel fibronectin recognition site within this sequence of tissue transglutaminase. Substitution of individual domains of tissue transglutaminase with those from homologous factor XIIIA showed that the major fibronectin-binding site is present within the first beta-sandwich domain of the protein. Experiments with deletion mutants of the first domain revealed that amino acids 81-140 of tissue transglutaminase are involved in fibronectin binding. Using synthetic peptides encompassing this region, we found that the peptide 88WTATVVDQQDCTLSLQLTT106 inhibited the interaction of tissue transglutaminase with fibronectin and decreased transglutaminase-dependent cell adhesion and spreading. In the three-dimensional structure of the first domain, amino acids 88-106 comprise an extended hairpin formed by antiparallel beta strands 5 and 6. Mutations of Asp94 and Asp97 within the beta5/beta6 hairpin to Ala significantly reduced the affinity of tissue transglutaminase for fibronectin, indicating that these residues are critical for fibronectin binding. Identification of the fibronectin-binding site on tissue transglutaminase will help to dissect the role of this protein in cell-matrix interactions.     

The role of galacturonic acid in outer membrane stability in Klebsiella pneumoniae

In most members of the Enterobacteriaceae, including Escherichia coli and Salmonella, the lipopolysaccharide core oligosaccharide backbone is modified by phosphoryl groups. The negative charges provided by these residues are important in maintaining the barrier function of the outer membrane. Mutants lacking the core heptose region and the phosphate residues display pleiotrophic defects collectively known as the deep-rough phenotype, characterized by changes in outer membrane structure and function. Klebsiella pneumoniae lacks phosphoryl residues in its core, but instead contains galacturonic acid. The goal of this study was to determine the contribution of galacturonic acid as a critical source of negative charge. A mutant was created lacking all galacturonic acid by targeting UDP-galacturonic acid precursor synthesis through a mutation in gla(KP). Gla(KP) is a K. pneumoniae UDP-galacturonic acid C4 epimerase providing UDP-galacturonic acid for core synthesis. The gla(KP) gene was inactivated and the structure of the mutant lipopolysaccharide was determined by mass spectrometry. The mutant displayed characteristics of a deep-rough phenotype, exhibiting a hypersensitivity to hydrophobic compounds and polymyxin B, an altered outer membrane profile, and the release of the periplasmic enzyme beta-lactamase. These results indicate that the negative charge provided by the carboxyl groups of galacturonic acid do play an equivalent role to the core oligosaccharide phosphate residues in establishing outer membrane integrity in E. coli and Salmonella.