Effect of a Short Peptide with Alternating L- and D-Amino Acid on the Aggregation and Membrane Damage of hIAPP

Alpha-sheet is believed to be a significant structural compo-nent, formed in the fibrillation process of the amyloid pep-tide. However, the knowledge about the role of a-sheet played in the amyloidosis and toxicity is lack. In this work, we modi-fied a short peptide derived from the core region of human islet amyloid polypetide(hIAPP, hIAPP18–27) with an alternating D-amino acid replacement and investigated the effects of the L/D alternating peptide on the fibrillar aggregation and the membrane damage of hIAPP using NMR, ThT fluorescence assay, circular dichroism(CD), transmission electron microscopy(TEM) and leakage assay, and com-pared the results with those of hIAPP18–27 without D-amino acid re-placement. We show that the short peptide with alternating L- and D-amino acids forms an a-sheet structure and is more potent in pro-moting the fibrillation of hIAPP and reducing the ability of hIAPP to disrupt the membrane composed of POPG and POPC[1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine] 1:4 lipids than the short pep-tide with all L-amino acids in a random coil structure. The higher po-tency of the D/L alternating peptide in these activities is attributed to its ability to induce the a-sheet-like structure in the core region of hIAPP and block the interaction of hIAPP with the membrane more effectively.