EVIDENCE FOR AN ALPHA-HELICAL T-CELL EPITOPE IN THE C-TERMINUS OF THEMAIN 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 ele ments found by analysing the Bet v 1 circular dichroism data. Accordin g to both experiment and prediction, 32% of 160 amino acids participat e in alpha helices, 21% in beta sheets, 24% in turns, and 23% in other structural motifs. The peptide LRAVESYLLAHS which represents one of t he major T cell epitopes on Bet v 1 was shown to have a high propensit y to form an alpha helix. Time-resolved fluorescence anisotropy measur ements of the allergen revealed an overall rotational correlation time of 7.35 ns, which corresponds to a hydrodynamic molecular radius of 1 9.2 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 spect rum. The results presented hen are in good agreement with the recently solved NMR structure of Amb t 5: both allergens are monomers in solut ion with an extended C-terminal alpha helix containing a major T cell epitope. (C) 1996 Academic Press, Inc.