The cell surfaces of bacteria are replete with diverse glycoconjugates that play pivotal roles in determining how bacteria interact with the environment and the hosts that they colonize. Studies to advance our understanding of these interactions rely on the availability of chemically defined glycoconjugates that can be selectively modified under orthogonal reaction conditions to serve as discrete ligands to probe biological interactions, in displayed arrays and as imaging agents. Herein, enzymes in the N-linked protein glycosylation (Pgl) pathway of Campylobacter jejuni are evaluated for their tolerance for azide-modified UDP-sugar substrates, including derivatives of 2,4-diacetamidobacillosamine and N-acetylgalactosamine. In vitro analyses reveal that chemoenzymatic approaches are useful for the preparation of undecaprenol diphosphate-linked glycans and glycopeptides with site-specific introduction of azide functionality for orthogonal labeling at three specific sites in the heptasaccharide glycan. The uniquely modified glycoconjugates represent valuable tools for investigating the roles of C. jejuni cell surface glycoconjugates in host pathogen interactions.
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http://dx.doi.org/10.1021/jacs.5b07146 | DOI Listing |
J Carbohydr Chem
April 2024
Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA.
Glycosylphosphatidylinositol (GPI) anchors contain a unique α-D-glucosamine-(1→6)--inositol [αGlcN(1,6)Ins] motif in their conserved core structure. To facilitate investigations of the functional roles of this structural motif, two GPI analogues containing unnatural βGlcN(1,6)Ins, instead of αGlcN(1,6)Ins, and an alkyne group at different positions of the GPI core were designed and synthesized. To this end, an orthogonally protected pseudopentasaccharide derivative of GPIs with the βGlcN(1,6)Ins motif was convergently constructed via [3+2] glycosylation and used as the common intermediate to prepare both GPI analogues by streamlined synthetic protocols.
View Article and Find Full Text PDFmBio
January 2025
Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
Many bacterial toxins exert their cytotoxic effects by enzymatically inactivating one or more cytosolic targets in host cells. To reach their intracellular targets, these toxins possess functional domains or subdomains that interact with and exploit various host factors and biological processes. Despite great progress in identifying many of the key host factors involved in the uptake of toxins, significant knowledge gaps remain as to how partially characterized and newly discovered microbial toxins exploit host factors or processes to intoxicate target cells.
View Article and Find Full Text PDFMany protein bioconjugation strategies focus on the modification of lysine residues owing to the nucleophilicity of their amine side-chain, the generally high abundance of lysine residues on a protein's surface and the ability to form robustly stable amide-based bioconjugates. However, the plethora of solvent accessible lysine residues, which often have similar reactivity, is a key inherent issue when searching for regioselectivity and/or controlled loading of an entity. A relevant example is the modification of antibodies and/or antibody fragments, whose conjugates offer potential for a wide variety of applications.
View Article and Find Full Text PDFDespite rapid advances in genomic sequencing, most rare genetic variants remain insufficiently characterized for clinical use, limiting the potential of personalized medicine. When classifying whether a variant is pathogenic, clinical labs adhere to diagnostic guidelines that comprehensively evaluate many forms of evidence including case data, computational predictions, and functional screening. While a substantial amount of clinical evidence has been developed for these variants, the majority cannot be definitively classified as 'pathogenic' or 'benign', and thus persist as 'Variants of Uncertain Significance' (VUS).
View Article and Find Full Text PDFBiophys Physicobiol
September 2024
Molecular and Cellular Biochemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan.
Single-molecule imaging provides information on diffusion dynamics, oligomerization, and protein-protein interactions in living cells. To simultaneously monitor different types of proteins at the single-molecule level, orthogonal fluorescent labeling methods with different photostable dyes are required. G-protein-coupled receptors (GPCRs), a major class of drug targets, are prototypical membrane receptors that have been studied using single-molecule imaging techniques.
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