Analysis of the secondary structure propensity of FADD DD (as determined using the program AGADIR31) suggests that the level of overall helical propensity is very low; only two regions of the protein, the N-terminal region of H4 and the C-terminal region of H6, show any significant helical propensity (> 10%). Interestingly, neither of these regions is involved in forming the central topology-defining core, although the N-terminal region of H4 appears to be important in the folding of B2.