Protein–Glycan Quinary Interactions in Crowding Environment Unveiled by NMR Spectroscopy

5 years ago

Protein–Glycan Quinary Interactions in Crowding Environment Unveiled by NMR Spectroscopy

Jesús Jiménez-Barbero, Filipa Marcelo, Ana Diniz, Eurico J. Cabrita, Jorge S. Dias

Protein–glycan interactions as modulators for quinary structures in crowding environments were explored. The interaction between human galectin 3 (Gal-3) and distinct macromolecular crowders, such as bovine and human serum albumin (BSA and HSA), Ficoll 70 and PEG3350, was scrutinized. The molecular recognition event of the specific ligand, lactose, by Gal-3 in crowding conditions was evaluated. Gal-3 interactions were monitored by NMR analysing chemical shift perturbation (CSP) and line broadening of 1H15N-HSQC signals. The intensity of the Gal-3 1H15N-HSQC signals decreased in the presence of all crowders, due to the increase in the solution viscosity and to the formation of large protein complexes. When glycosylated containing samples of BSA and HSA were used, signal broadening was more severe than that observed in the presence of the more viscous solutions of PEG3350 and Ficoll 70. However, for the samples containing glycoproteins, the signal intensity of 1H15N-HSQC recovered upon addition of lactose. We show that serum proteins interact with Gal-3, through their α2,3-linked sialylgalactose moieties exposed at their surfaces, competing with lactose for the same binding site. The quinary interaction between Gal-3 and serum glycoproteins, could help to co-localize Gal-3 at the cell surface, and may play a role in adhesion and signalling functions of this protein. Glycosylation as key player for quinary structure in crowding environments: Glycan-mediated human galectin 3 (Gal-3) and serum protein interactions strongly affect the dynamics of Gal-3, as proven by the NMR experiments in crowding conditions. Gal-3 binds through α2,3-sialylgalactose chains present in serum glycoproteins competing with lactose binding site. Gal-3/serum protein quinary structure could help to co-localize Gal-3 at the cell surface and may have implications in adhesion and signalling functions of this protein.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201702800