Ligand Binding Modulates the Structural Dynamics and Compactness of the Major Birch Pollen Allergen

Abstract

Pathogenesis-related plant proteins of class-10 (PR-10) are essential for storage and transport of small molecules. A prominent member of the PR-10 family, the major birch pollen allergen Bet v 1, is the main cause of spring pollinosis in the temperate climate zone of the northern hemisphere. Bet v 1 binds various ligand molecules to its internal cavity, and immunologic effects of the presence of ligand have been discussed. However, the mechanism of binding has remained elusive. In this study, we show that in solution Bet v 1.0101 is conformationally heterogeneous and cannot be represented by a single structure. NMR relaxation data suggest that structural dynamics are fundamental for ligand access to the protein interior. Complex formation then leads to significant rigidification of the protein along with a compaction of its 3D structure. The data presented herein provide a structural basis for understanding the immunogenic and allergenic potential of ligand binding to Bet v 1 allergens.

Dynamics Rationalize Proteolytic Susceptibility of the Major Birch Pollen Allergen Bet v 1

“…However, in describing the Bet v 1 variants as conformational ensembles we find a coherent link between local unfolding probability and proteolytic susceptibility. In many experimental and computational studies this relation has already been debated (Parsell and Sauer, 1989;Thai et al, 2004;Ohkuri et al, 2010;Asam et al, 2014;Grutsch et al, 2014Grutsch et al, , 2017Scheiblhofer et al, 2017). Yet, to the best of our knowledge, to this point no structural model of a partially unfolded state has been suggested.…”

“…As described above, Bet v 1 is among the most extensively studied allergen proteins in experiment, computational models and clinical studies (Spangfort et al, 2003;Bollen et al, 2010;Berkner et al, 2014;Garrido-Arandia et al, 2014;Grutsch et al, 2014;Kitzmuller et al, 2015;Kamenik et al, 2016;Moingeon et al, 2016;Biedermann et al, 2019). With an estimated 100 million of individuals suffering from birch pollen allergy, it is also one of the clinically most relevant allergens (Hartl et al, 2004).…”

Conformational Flexibility Differentiates Naturally Occurring Bet v 1 Isoforms

“…Differences between the involved structures are small, ruling out segmental unfolding of the protein backbone [26]. Rather, the structural flexibility on this time scale is reminiscent of “conformational breathing” of the protein scaffold [27], as reported for various lipid binding proteins and lipocalins [28,29,30].…”

Measurement of Ligand–Target Residence Times by 1H Relaxation Dispersion NMR Spectroscopy

“…47,48 Purities were determined by electrospray ionization mass spectrometry (purity ≥95% for all targets). Bovine serum albumin (BSA) and bovine trypsin were purchased from Sigma-Aldrich (100% pure, as determined by agarose electrophoresis and UV spectroscopy, respectively; see Supporing Information).…”