Evidence for an alpha helical T cell epitope in the C-terminus of the main birch pollen allergen bet V 1

Secondary structure prediction of the main birch pollen allergen Bet v 1 was found to be in good agreement with the secondary structural elements found by analysing the Bet v 1 circular dichroism data. According to both experiment and prediction, 32% of 160 amino acids participate in alpha helices, 21% in beta sheets, 24% in turns, and 23% in other structural motifs. The peptide LRAVESYLLAHS which represents one of the major T cell epitopes on Bet v 1 was shown to have a high propensity to form an alpha helix. Time-resolved fluorescence anisotropy measurements of the allergen revealed an overall rotational correlation time of 7.35 ns, which corresponds to a hydrodynamic molecular radius of 19.2 Angstrom. This refers to a monomeric Bet v 1 molecule in solution, which is also reflected in the narrow band width of the H-1-NMR spectrum. The results presented hen are in good agreement with the recently solved NMR structure of Amb t 5: both allergens are monomers in solution with an extended C-terminal alpha helix containing a major T cell epitope. (C) 1996 Academic Press, Inc.