Molecular and supramolecular studies on polyglycine and poly-l-proline

Abstract

Elastin is a cross-linked protein, whose soluble precursor is tropoelastin, responsible for resilience and elastic recoil in vertebrate tissues. Glycine and proline are among the most repeated amino acids in tropoelastin primary structure, the high flexible glycine being present 222 times and the more constrained proline being present 96 times. In order to deeper investigate the role of glycine and proline residues in elastin, we studied the molecular and supramolecular structures of polyglycine and poly-L-proline homopolypeptides as significant sequences for the protein. As a matter of fact, up to now, if few conformational studies are accessible only for poly-L-proline homopolypeptide in solution and for polyglycine homopolypeptide in the solid state, limited supramolecular studies are available for both homopolypeptides. Given the self-aggregation properties of these homopolypeptides, we investigated the aggregation mechanism by turbidimetry measurements together with Congo red birefringence assay, ThT fluorescence spectroscopy, and atomic force microscopy and transmission electron microscopy studies. At molecular level, we show the dominance of the cross-b structure for polyglycine fibrils while for poly-L-proline aggregates PPII conformation prevails. At supramolecular level, the results show that polyglycine is able to self-aggregate into amyloid-like fibres while poly-L-proline aggregates by following a specific pathway ranging from protofibrils to fibrils. These findings suggest that the self-aggregation properties of elastin are influenced by tropoelastin primary structure thus explaining why glycine-rich elastin-derived polypeptide sequences are amyloidogenic (Gly-effect) while proline-rich elastin-derived polypeptide sequences (Pro-effect) are able to coacervate.

Tunable Thermoresponsiveness of Resilin via Coassembly with Rigid Biopolymers

“…This is consistent with the study by Lorusso et al that reported the morphology of PP on silicon wafer to be globular aggregates that evolve into protofibrils. 13 The Rec1-resilin/PP system showed increased roughness values and larger elongated PP aggregates distributed throughout the Rec1-resilin matrix ( Figure 4C), which is in agreement with the DLS data that revealed structures of increasing size and the two distinct peaks of smaller individual particles and larger aggregated groups (Supporting Information S5,S6). The line curve indicates that the larger aggregates have a height of approximately 2 to 5 nm, which is in agreement with the known behavior of PP ( Figure 4C).…”

“…Poly-L-proline was chosen as the steric constraints present in the structure that results in the PPII helix are shown to be important for temperatureinduced coacervation. 13 The purpose was to investigate the effect of a model system (PP) on inducing structural changes of the coassembly, in this case induction of PPII helix formation. The molecular weight, 10.7 kDa, was chosen because the size is appropriate for interactions with Rec1-resilin of molecular weight 28.4 kDa.…”

“…Lorusso et al reported that prolinerich domains that form stable PPII structures are responsible for the self-assembling coacervation process of the tropoelastin molecule. 13 Therefore, the higher propensity for coacervation and lower LCST observed for the Rec1-resilin/PP coassembly can be attributed to the achievement of a more stable PPII conformation.…”

Do habitat features affect the composition of silk proteins by Namibian arid-adaptedAriadnaspiders (Araneae: Segestriidae)?

“…On the basis of the data in the literature (Moore & Krimm 1976;Jackson and Mantsch 1995;Bramanti et al 2005;Papadopoulos et al 2007;Lorusso et al 2011) and, in particular, according to published FT-IR spectra of glycine-and alanine-based polypeptides, we affirm that the HFIP extracts the protein constituting the spider silk. In fact, the absorption bands i the 1600-1700 cm −1 and 1480-1600 cm −1 regions assigned to the characteristic vibrational modes of the amide (-CONH) groups fit well with the so-called amide II and amide I absorptions of proteins, respectively.…”

“…The less intense peak at about 1260 cm −1 was assigned to amide III and is due to the C-N stretching coupled to the in-plane N-H bending mode. Typical absorption bands due to the stretching of the N-H bond (ν N-H ) appear at about 3295 and 3100 cm −1 and are referred as amide A and B, respectively (Moore & Krimm 1976;Jackson & Mantsch 1995;Bramanti et al 2005;Papadopoulos et al 2007;Lorusso et al 2011). A large band due to the stretching of O-H moieties appears between 3400 and 3700 cm −1 .…”