Stability of the C-terminal peptide of CETP mediated through an (i, i + 4) array

Based on circular dichroism (CD), we have found an essential (i, i + 4) alpha-helix stabilizing array in the C-terminus region for the cholesteryl ester transfer protein (CETP) between histidine 466 and aspartic acid 470. This region apparently corresponds to an amphipathic alpha-helix. The behavior of this peptide in solution in comparison with a mutant peptide (D470N) was also analyzed by dynamic light scattering (DLS). The results showed that alpha-helix stabilization is not due to peptide aggregation. The thermodynamic estimation of stability supports the idea that the phenomenon is carried out through an (i, i + 4) array. The representation of the C-terminal region as an amphipathic alpha-helical peptide shows that lipid-binding activity might be in part due to both the asymmetric polar/non-polar residue distribution and to the presence of an (i, i + 4) array important for helix stability.