The secondary structure of birch pollen profilin, a potent human allergen, was elucidated by multidimensional nuclear magnetic resonance (NMR), as a prerequisite to study the interaction of this profilin with ligands for its poly-(l-proline) (PLP)-binding site. The chemical shifts of the 15N-labeled backbone amide groups were used to monitor complex formation with various PLP peptides. Titration with deca-l-proline (P10) yielded a K D of 0.2 mM. P8 was the shortest PLP to provoke a significant reaction. (GP5)3G bound significantly, confirming the interaction between profilins and the protein VASP containing this motif. Birch profilin interacted also with GP6GP5, found in the cyclase-associated protein (CAP), a suspected profilin ligand.
