Biology subjects

Twine, S. M.

Publications and source records attributed to Twine, S. M..

4 recordsLinked to original sources

bioRxiv2024

Characterizing putative glycosyltransferases within the flagella glycosylation island (FGI) of Aeromonas hydrophila ATCC 7966T

Motility is an important virulence factor for many pathogenic bacteria, enabling locomotion towards favourable conditions and away from hostile environments. Flagellar-mediated motility is driven by one or more flagellar filaments that extend outside of the cell and rapidly rotate to generate movement. These filaments are assembled through the polymerization of thousands of copies of structural flagellin proteins. It has been shown that flagellin glycosylation is often a prerequisite for proper flagella structure and function. Aeromonas hydrophila ATCC 7966T, a clinical and environmental pathogen, elaborates a single polar flagellum. The polar flagellin structural proteins FlaA and FlaB are glycosylated with a heterologous collection of complex penta- and hexa-saccharide chains. This study characterized the involvement of four genes with homology to known glycosyltransferases located within the A. hydrophila ATCC 7966T flagellar glycosylation island (FGI) in the biosynthesis of the complex polysaccharide glycans modifying the polar flagellins. Deletion of genes AHA_4167, AHA_4169, AHA_4170, and AHA_4171 were observed to have truncated glycans with sequentially shorter chain length, and all of these mutant strains had reduced motility compared to wild type bacteria.

biochemistry↗

bioRxiv2024

Polar flagellin glycan metaheterogeneity of Aeromonas hydrophila strain ATCC 7966T

Motile pathogens often rely upon flagellar motility as an essential virulence factor and in many species the structural flagellin protein is glycosylated. This post-translational modification has been shown to be necessary for proper folding of the flagellin structural proteins and proper function of the flagellar filament in a number of bacterial species. Aeromonas hydrophila is a ubiquitous aquatic pathogen with a constitutively expressed polar flagellum. Using a suite of mass spectrometry techniques, the flagellin FlaA and FlaB structural proteins of A. hydrophila strain ATCC 7966T were shown to be glycosylated with significant metaheterogeneity: heterologous glycans were observed with variable site occupancy. The penta- and hexa-saccharide glycan chains contained a previously unreported pseudaminic acid derivative with a mass of 422 Da as the linking sugar, followed in sequence by two hexoses, an N-acetylglucosamine derivative, a deoxy N-acetylglucosamine derivative, and sometimes an additional N-acetylglucosamine.

biochemistry↗

bioRxiv2022

Integrated Immunopeptidomics and Proteomics Study Reveals Imbalanced Innate and Adaptive Immune Responses to SARS-Cov-2 Infection

We present an integrated immunopeptidomics and proteomics study of SARS-Cov-2 infection to comprehensively decipher the changes in host cells in response to viral infection. Our results indicated that innate immune response in Calu-3 cells was initiated by TLR3, followed by activation of interferon signaling pathway. Host cells also present viral antigens to the cell surface through both Class I and Class II MHC system for recognition by adaptive immune system. SARS-Cov-2 infection led to the disruption of antigen presentation as demonstrated by higher level of HLA proteins from the flow-through of MHC immunoprecipitation. Glycosylation analysis of HLA proteins from the elution and flow-through of immunoprecipitation revealed that the synthesis and degradation of HLA protein was affected by SARS-Cov-2 infection. This study provided many useful information to study the host response to SARS-Cov-2 infection and would be helpful for the development of therapeutics and vaccine for Covid-19 and future pandemic.

immunology↗

bioRxiv2022

Safety and uptake of fully oxidized β-carotene

Spontaneous oxidation of {beta}-carotene yields a polymer-rich product (OxBC) also containing small amounts of many apocarotenoids. OxBC extends {beta}-carotenes benefits beyond vitamin A, finding utility in supporting health in livestock, pets, and humans. Although naturally occurring OxBC is consumed in foods and feeds, a direct demonstration here of safety of synthetic OxBC supports its increasing usage. A toxicological study in rats showed a maximum tolerated single oral dose, an LD50, and a NOAEL of 5,000, 30,079 and 1875 mg/kg body weight, respectively. The repeat-dose 90-day oral toxicity study showed no adverse physiological or pathological effects. A first study of OxBC uptake by mice over 2-5 days into a select set of tissues showed OxBC already was naturally present. The highest levels were in liver, lung, and hamstring. Despite dosing, no net increases occurred in liver, kidney, lung, and muscle. Net increases occurred in urine, intestinal content, plasma, feces, spleen, and cecum, consistent with processing of OxBC and preferential elimination of polymer. Compared to the 4:1 polymer: apocarotenoid ratio of OxBC, polymer was enriched in liver and spleen and depleted in lung, kidney, hamstring, and abdominal muscle. The apparent control of OxBC in major tissues further supports its safety.

pharmacology and toxicology↗