Serial crystallography and kinetics reveal how the FimH bacterial lectin tweaks between mono‐ and multivalent binding of high‐mannose N‐glycans

Abstract

BackgroundThe lectin domain of the fimbrial adhesin FimH from Escherichia coli recognizes with the highest affinity and in seemingly monovalent fashion oligomannosides‐3 and ‐5 N‐glycans. This happens with a high affinity (Kd=20 nM) because the alpha1,3‐linked arm remains free from any further alpha1,2‐mannose substitution. The latter causes an at least 10‐fold affinity loss in creating the oligomannose‐6 N‐glycan (1).MethodsThe binding of FimH to pauci‐ and oligomannoside‐containing N‐glycans and similarly glycosylated proteins, as well as its dimannoside endings Manalpha1,2, Manalpha1,3 and Manalpha1,6, have been profiled using the FimH Lectprofile kit (GlycoDiag, Applied Glycomics, France) and a newly designed paucimannose‐containing glycan array. The kinetics of binding, ka and kd, were analysed using surface plasmon resonance and compared with earlier incomplete data (2).ResultsMono‐ and multivalent binding were found in co‐crystal structures of the FimH lectin domain with alpha1,6‐fucosylated oligomannose‐3 and with oligoannose‐6, respectively. The kinetics of binding indicate that once alpha1,2‐linked mannose comes into play, the complexes are not so stable, as previously also measured using calorimetry (3), and accompanied with a high dissociation constant. Molecular dynamics simulations further support that it is not the total interaction energy that determines the final retained complex (metastable complexes), but the kinetics of interaction with the three possible dimannoside endings.ConclusionsKinetics and stability of the complexes drive the most favoured arrangement, via either a unique or multivalent interaction, between the N‐glycan and the FimH protein in the crystal.References :(1) Bouckaert, J., Mackenzie, J., de Paz, J. L., Chipwaza, B., Choudhury, D., Zavialov, A., Mannerstedt, K., Anderson, J., Pierard, D., Wyns, L., Seeberger, P. H., Oscarson, S., De Greve, H., Knight, S. D. (2006) The affinity of the FimH fimbrial adhesin is receptor‐driven and quasi‐independent of Escherichia colipathotypes. Molecular Microbiology 61, 1556‐1568(2) Sauer, M. M., Jakob, R. P., Luber, T., Canonica, F., Navarra, G., Ernst, B., Maier, T., Glockshuber, R. (2019) Binding of the bacterial adhesin FimH to its natural, multivalent high‐mannose type glycan targets. J Am Chem Soc 141, 936‐944(3) Dumych, T., Bridot, C., Gouin, S. G., Paryzhak, S., Szunerits, S., Bilyy, R., Bouckaert, J., (2018) A novel integrated way for deciphering the glycan code for the FimH lectin. Molecules 23, 2794