Decorin binding proteins from European Borrelia – do structural differences influence ligand binding?

Libor Hejduk1,2, Petr Rathner3,#, Martin Strnad1,2, Filip Dyčka1,  Libor Grubhoffer1,2, Ján Štěrba1, Ryan O. M. Rego1,2, Norbert Müller1, Adriana Rathner4

1Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czech Republic

2Institute of Parasitology, Biology Centre, Czech Academy of Sciences, 37005 České Budějovice, Czech Republic

3Institute of Inorganic Chemistry, Johannes Kepler University, 4040 Linz, Austria

4Institute of Biochemistry, Johannes Kepler University, 4040 Linz, Austria

#Present address: Institute of Analytical Chemistry, University of Vienna, 1090 Vienna, Austria

 

Adhesion of spirochetes from Borrelia burgdorferi sensu lato complex is the crucial step in early phase of Lyme disease infection. Decorin binding proteins (Dbp) are glycosaminoglycan (GAG) binding adhesins exposed on the surface of borrelia spirochetes. Dbps are expressed in two homologous forms A and B, both of them were characterized as main factors of borrelia virulence(1). Based on the previous described differences in binding mechanisms of Dbp-GAG interaction (2), we focused on the relations between structural differences and GAG binding. We aim to describe the structural differences in detail among Dbps from european Borelia species and their particular interactions with different GAGs using solution nuclear magnetic resonance (NMR) spectroscopy at atomic resolution. Almost complete backbone and sidechain assignments of DbpA from B. Afzelii and B. Bavariensis have been achieved. Predictions of secondary structure propensity for both variants, calculated from assigned chemical shifts, were compared with available NMR structures of North American borrelia species. Backbone dynamics was described by T1 and T2 spin relaxations and 1H 15N heteronuclear NOE (Nuclear Overhauser effect) experiments. We performed initial protein-GAG interaction studies of both variants of DbpA with different GAGs by NMR titrations including protein dynamics measurement by heteronuclear NOE experiments, hydrogen-deuterium exchange mass spectrometry (HDX-MS) and surface plasmon resonance (SPR) trial measurement. NMR-based prediction of secondary structure propensity and protein backbone dynamics combined with initial protein-ligand interaction experiments, which indicates interspecific differences in GAG binding, provided insight into structural characteristics of DbpA and will set the starting point for future extensive research of specific differences in structure and dynamics of Dbps and how it influence the interaction mechanism with GAG ligands.

1. Lin Y P, Benoit V, Yang X, Martínez-Herranz R, Pal U, & Leong J M (2014). Strain-specific variation of the decorin-binding adhesin DbpA influences the tissue tropism of the lyme disease spirochete. PLoS pathogens, 10(7)

2. Morgan A M, & Wang X (2015). Structural mechanisms underlying sequence-dependent variations in GAG affinities of decorin binding protein A, a Borrelia burgdorferi adhesin. The Biochemical journal, 467(3), 439–451.

3. Hejduk L, Rathner P, Strnad M, Grubhoffer L, Sterba J, Rego R.O.M., Müller N, Rathner A (2021). Resonance assignment and secondary structure of DbpA protein from the European species, Borrelia afzelii. Biomolecular NMR assignments, 15(2), 415–420.