On the occurrence of polyproline II structure in elastin

To shed light on the occurrence of the polyproline II (PP II) structure in the elastomeric protein elastin, the octapeptide sequence ALGGGALG of the N -terminal region of human elastin was studied in its monomeric and polymeri c form, both in solution and in the solid state. Furthermore, the polymer p oly(PG), chosen by us as an a priori reference compound for investigating t he stability of PP II structure in presence of alternating proline and glyc ine residues along the polypeptide chain, was studied by circular dichroism (CD) and Fourier transform infrared F-IR) spectroscopy. Its "monomeric" fo rm Boc-PG-OH, was also analyzed by X-ray diffraction. It was shown that, in the solid state the presence of PG or GGG sequences in polypeptide chains and even in a short peptide as Boc-PG-OH induces the acquisition of the PP II structural motif. However, in solution this conformation appears to be m uch more unstable even in the case of long polypeptide chains. The finding that at room temperature the PP II structure is always in equilibrium with other conformers suggests that its dynamics could also contribute to the mo lecular mechanism of elastin elasticity. (C) 2000 Elsevier Science Ltd. All rights reserved.