(323g) The Effect of Heteromultivalency on Lectin-Glycan Binding Process and the Identification of Critical Parameter

Glycans are the most diverse fundamental cellular macromolecules that form complex patches over the cell surfaces and bind with lectins (i.e., glycan-binding protein) [1]. The glycan-lectin binding process is important as a wide range of microbial reactions such as bacterial adhesion, viral infection, and cell differentiation, are involved with this [1-3]. One of the unique characteristics of the glycan-lectin binding process is that a single lectin often contains multiple binding pockets interacting with multiple glycan molecules (i.e. multivalency) [1,4]. We recently found that the two dimensional diffusion of glycan molecules on a cell membrane allows a homo-oligomeric lectin simultaneously binds to different types of glycans. This hetero-multivalent binding process alters the lectin binding behaviors, including binding kinetics, energy, and capacity. A living organism may utilize the hetero-multivalency to control the downstream biochemical reactions. In order to understand the role of heteromultivalency in biological processes, a new theoretical approach is needed to model this complex process.

We developed a kinetic Monte Carlo (kMC) simulation, which only relies on the fundamental physics/chemistry principles, to model the process of lectin binding to glycans on cell surfaces. The kMC simulation only considered three universal principles: binding, unbinding and diffusion [5-6]. The kMC simulation allows us to monitor the heteromultivalent binding process and the variation of binding configurations in detail. We observed that the high-affinity glycan ligands can facilitate lectin binding to other low-affinity glycan ligands on a cell membrane. Even though these low-affinity ligands are barely detectable in microarrays where ligands are immobilized, the two dimensional ligand diffusion could activate the interactions between a bound lectin and low-affinity ligands, leading to the changes in binding behaviors. To explore the critical parameters influencing heteromutivalency, we varied the glycan affinity, density, and diffusion rate in the simulations. We observed that a threshold density of low-affinity glycan ligands is required to trigger heteromultivalent binding process. Our work explains why lectin functions sometime are controlled by low-affinity ligands. In contrast to molecular dynamic simulation, the kMC simulation that can model a longer time scales (up to hours) is a better method to study the influence of relatively slow dynamics of glycan diffusion.

References

[1] Varki A. Biological roles of glycans. Glycobiology, 2017, 27, 3-49.

[2] Branson TR.; McAllister TE.; Garcia-Hartjes J.; Fascione MA.; Ross JF.; Warriner SL.; Wennekes T.; Zuilhof H.; Turnbull WB. A proteinbased pentavalent inhibitor of the cholera toxin B-subunit. Angew. Chem. Int. Ed. Engl., 2014, 53, 8323–8327.

[3] Worstell NC.; Singla A.; Saenkham P.; Galbadage T.; Sule P.; Lee D.; Mohr A.; Kwon JSI.; Cirillo JD.; Wu HJ. Hetero-multivalency of Pseudomonas aeruginosa lectin LecA binding to model membranes. Sci. Rep., 2018, 8, 8419.

[4] Worstell NC.; Singla A.; Wu HJ. Evaluation of hetero-multivalent lectin binding using a turbidity-based emulsion agglutination assay. Colloids Surf. B Biointerfaces., 2019, 175, 84–90.

[5] Fallahi-Sichani M.; Linderman JJ. Lipid raft-mediated regulation of G-protein coupled receptor signaling by ligands which influence receptor dimerization: A computational study. PLoS One., 2009, 4, e6604.

[6] Lee D.; Mohr A.; Kwon JSI. Kinetic Monte Carlo modeling of multivariant binding of CTB proteins with GM1 receptor. Comp. Chem. Eng., 2018, 118, 283-295.