Fig. 4. Lithostathine tetramer. (A) Superimposition of lithostathine and TN3 backbones. Lithostathine backbone is in yellow, TN3 backbone is in white. The greatest differences can be seen to lie in the N-terminal extremities and in the loop regions. (B) Model for tetrameric lithostathine obtained after superimposition of TN3 tetramer and energy minimization. Hydrophobic sheets containing aromatic residues (24–33 and 136–143) are shown in red. The H2 helix (35–45) is in blue and the H3 helix (56–68) in green. The majority of the hydrophobic residues are located inside the tetramer. Interestingly, it can be noted that in the H3 helix lithostathine showed a four-residue motif, 59-GAFV-62, which commonly occurs among amyloidogenic proteins such as the islet amyloid polypeptide, the Aβ peptide, the non-amyloid component of Alzheimer’s disease and the prion protein (El-Agnaf and Irvine, 2000).