Molecular and supramolecular structural studies on significant repetitive sequences of resilin

Resilin is a member of the family of elastomeric proteins and is found in specialised regions of the cuticle of most insects, and provides low stiffness, high strain and efficient energy storage. It is best known for its role in insect flight and the remarkable jumping ability of fleas and spittle bugs. In common with other elastomeric proteins, the recently identified Drosophila melanogaster proresilin shows glycine-rich repetitive sequences; in particular the N- and C-terminal regions of the protein are dominated by 18 repeats of a 15-residue sequence (SDTYGAPGGGNGGRP) and eleven repeats of a 13-residue sequence (GYSGGRPGGQDLG), respectively. We synthesised and analysed the molecular and supramolecular structure of some polypeptides with sequences belonging to the glycine-rich repeated domain of D. melanogaster resilin. The conformational studies performed by CD, FTIR and NMR spectroscopies pointed to the coexistence of two main conformational features, such as folded beta-turns and (quasi)extended structures (e.g., poly-L-proline II conformation) in common with other elastomeric proteins; this suggests an elasticity mechanism for resilin common to other elastomeric proteins. Our data show that also in the case of resilin, repetitive sequences are characterised by autonomous structures almost independent of the remaining parts of the molecule as already extensively found for elastin. From a supramolecular point of view, a great tendency to aggregate in fibrous structures is observed, particularly for the resilin- inspired polypeptide (PGGGN)(10). This is encouraging for the development of resilin-based biomaterials for the production of biocompatible medical devices, as well as high performing elastic materials.