Validation of Reactivity Descriptors to Assess the Aromatic Stacking within the Tyrosine Gate of FimH

Antagonists of the FimH adhesin, a protein almost universally present at the extremity of type-1 fimbriae expressed by <i>Escherichia coli</i>, have been abundantly in the spotlight as alternative treatments of urinary tract infections. The antagonists function as bacterial antiadhesives through highly specific α-d-mannose binding in a charged and polar pocket at the tip of the FimH lectin domain and by the stacking of alkyl or aromatic moieties substituted on the mannose with two tyrosine residues (Tyr48 and Tyr137) at the entrance of the mannose-binding pocket. Using high-resolution crystal data, interaction energies are calculated for the different observed aromatic stacking modes between the tyrosines and the antagonist. The dispersion component of the interaction energy correlates with the observed electron density. The quantum chemical reactivity descriptors local hardness and polarizability were successfully validated as prediction tools for ligand affinity in the tyrosine gate of FimH and therefore have potential for rapid drug screening

Mapping the Expressed Glycome and Glycosyltransferases of Zebrafish Liver Cells as a Relevant Model System for Glycosylation Studies

The emergence of zebrafish as a model organism for human diseases was accompanied by the development of cellular model systems that extended the possibilities for <i>in vitro</i> manipulation and <i>in vivo</i> studies after cell implantation. The exploitation of zebrafish cell systems is, however, still hampered by the lack of genomic and biochemical data. Here, we lay a path toward the efficient use of ZFL, a zebrafish liver-derived cell system, as a platform for studying glycosylation. To achieve this, we established the glycomic profile of ZFL by a combination of mass spectrometry and NMR. We demonstrated that glycoproteins were substituted by highly sialylated multiantennary <i>N</i>-glycans, some of them comprising the unusual zebrafish epitope Galβ1–4­[Neu5Ac­(α2,3)]­Galβ1–4­[Fuc­(α1,3)]­GlcNAc, and core 1 multisialylated <i>O</i>-glycans. Similarly, these analyses established that glycolipids were dominated by sialylated gangliosides. In parallel, analyzing the expression patterns of all putative sialyl- and fucosyltransferases, we directly correlated the identified structures to the set of enzymes involved in ZFL glycome. Finally, we demonstrated that this cell system was amenable to metabolic labeling using functionalized monosaccharides that permit <i>in vivo</i> imaging of glycosylation processes. Altogether, glycomics, genomics, and functional studies established ZFL as a relevant cellular model for the study of glycosylation