Sites for Dynamic Protein-Carbohydrate Interactions of O- and C-Linked Mannosides on the E. coli FimH Adhesin

Abstract

Antagonists of the Escherichia coli type-1 fimbrial adhesin FimH are recognized as attractive alternatives for antibiotic therapies and prophylaxes against acute and recurrent bacterial infections. In this study α-d-mannopyranosides O- or C-linked with an alkyl, alkene, alkyne, thioalkyl, amide, or sulfonamide were investigated to fit a hydrophobic substituent with up to two aryl groups within the tyrosine gate emerging from the mannose-binding pocket of FimH. The results were summarized into a set of structure-activity relationships to be used in FimH-targeted inhibitor design: alkene linkers gave an improved affinity and inhibitory potential, because of their relative flexibility combined with a favourable interaction with isoleucine-52 located in the middle of the tyrosine gate. Of particular interest is a C-linked mannoside, alkene-linked to an ortho-substituted biphenyl that has an affinity similar to its O-mannosidic analog but superior to its para-substituted analog. Docking of its high-resolution NMR solution structure to the FimH adhesin indicated that its ultimate, ortho-placed phenyl ring is able to interact with isoleucine-13, located in the clamp loop that undergoes conformational changes under shear force exerted on the bacteria. Molecular dynamics simulations confirmed that a subpopulation of the C-mannoside conformers is able to interact in this secondary binding site of FimH.

d-Mannose Treatment neither Affects Uropathogenic Escherichia coli Properties nor Induces Stable FimH Modifications

“…UPEC adhesion relies mainly on the interaction between FimH and mannosylated uroplakin proteins on the luminal surfaces of urothelial cells as well as other cellular receptors such as integrins [1,5,8,[13][14][15]. Therefore, FimH antagonists, such as d-mannose, have gained increasing consideration and proven to be effective for the treatment and/or prevention of acute and recurrent UPEC-mediated UTIs [21,22,[24][25][26][27]. Furthermore, d-mannose represents a real alternative to antibiotic regimens, reducing the burden of antibiotic resistance and associated side effects [2,14,31,[34][35][36].…”

“…For this reason, molecules able to interfere with bacterial virulence mechanisms have been proposed to combat UPEC infections [20]. Accordingly, FimH antagonists, such as d-mannose and its derivatives, have emerged as anti-virulence therapeutic strategies for the treatment of UTIs [21][22][23][24][25][26][27]. d-mannose, a C-2 epimer of d-glucose, as well as d-mannose-analogs, prevent FimH-mediated bacterial adhesion through a competitive inhibition mechanism [18,21,22,24,28].…”

Effect of Dendrimer Generation and Aglyconic Linkers on the Binding Properties of Mannosylated Dendrimers Prepared by a Combined Convergent and Onion Peel Approach

“…Amongst these, heptyl α- d -mannopyranoside (HM) as emerged as one of the strongest monovalent FimH binders described so far [ 3 ]. The studies supported that the hydrophobic HM’s aglycone strongly interacted via van der Waals contacts and aromatic stacking with the tyrosine gates residues Tyr148 and Tyr137 [ 2 , 8 , 13 ].…”

“…Besides, as the first defense mechanism against this infectious agent, the innate immune system exploits the structures of mannosides [ 4 , 5 ]. On the other hand, fimbriated E. coli receptor-binding site (FimH) consists of a specific mannose-binding pocket, with a tyrosine gate (Tyr48, Tyr137) [ 6 , 7 , 8 ] that also recognizes and binds to the mannosides residues of uroplakin-1a, present at the surface of urothelial cells as a premise for bacterial infections causing cystitis and pyelonephritis. Ever since, considerable efforts have been devoted toward the development of new synthetic antiadhesive antagonists that could act as potent competitive inhibitors [ 9 , 10 , 11 , 12 , 13 ].…”

The Inclusion of Water Molecules in Residue Interaction Networks Identifies Additional Central Residues

“…An active role for water has indeed been established in substrate binding to protein O-fucosyltransferase 2, where the binding mechanism involves a dynamic network of water-mediated interactions (Valero-González et al, 2016 ). Also for non-enzymatic substrate binding water can play an essential role, as evidenced by the crystal structure of the bacterial adhesin FimH, where a water molecule is found completely buried between the ligand and its binding pocket, engaging in hydrogen bonding to three protein residues and a hydroxyl group of the mannose ligand (Wellens et al, 2008 ; Touaibia et al, 2017 ).…”