Dissection of Human Tropoelastin: Solution Structure, Dynamics and Self‐Assembly of the Exon 5 Peptide

Abstract

The elastic properties of elastin have essentially been discussed in terms of dominant entropic components, with questions still remaining about whether the basic mechanism is compatible with the classical theory of rubber elasticity. A better understanding of the structure-function relationships in terms of the protein's elastic properties remains an important goal in elastin science. Recently, we succeeded in the exon-by-exon synthesis of all polypeptide sequences encoded by the so-called hydrophobic exons and almost all of the cross-linking exons of human tropoelastin. Among these, the peptide encoded by exon 5 (PGGLAGAGLGA) has been extensively studied by classical spectroscopic methods, such as CD and NMR spectroscopy, and by molecular dynamics simulations. The results obtained clearly evidenced a large flexibility of the polypeptide chain, which oscillates between rather extended conformations, such as PPII, and folded ones, such as beta turns. At the supramolecular level, we obtained evidence by TEM that shows that the peptide encoded by exon 5 is able to self-assemble in fibrillar structures, a result indicating that the "information" for self-assembly is also contained within a small domain of tropoelastin.

Investigating by CD the molecular mechanism of elasticity of elastomeric proteins

“…Basically, one could do careful measuring of Noe volumes of sequential and intraresidue Ha-HN NOE crosspeaks. 3,34 This volume ratio analysis requires reduced overlap of the signals, difficult to find for glycine-rich elastomeric peptides. On the other hand, the method put forward by Lam and Hsu 55 is interesting; however it requires further validation before becoming a standard protocol.…”

“…The study of the individual exons encoding an independent and selfcontained structure has been called the ''reductionist approach'' and has been shown to work in a series of papers. [14][15][16][30][31][32][33][34] Obviously, this approach will not apply to globular proteins where the concept of autonomous domains is usually not applicable. However, even in the case of elastin some scepticism could be present.…”

Circular dichroism studies on repeating polypeptide sequences of abductin

“…The choice of these solvents has been rationalized in previous papers. 4,5 Boc-MG-OH. 1 N NaOH (160 ml) was added to a solution of 0.160 mol of Boc-MG-OEt in acetone (36 ml).…”

“…2,3 In the latter case, CD (and NMR) spectroscopy allowed the proposal of a new molecular model of elasticity based on dynamic equilibria between extended (PPII, b-strands) and folded (b-turn) conformations. 4,5 Within the framework of this research area, we decided to apply the same approach to abductin, the protein responsible for compressive elasticity for the abductor ligament in bivalves. 6 The known conceptual amino acid sequence of abductin derived from Argopecten irradians 7 revealed the presence of three prominent amino acids: glycine, methionine, and phenylalanine ( Fig.…”

Supramolecular Amyloid-like Assembly of the Polypeptide Sequence Coded by Exon 30 of Human Tropoelastin

“…Although, the ability of the elastin precursor molecule to undergo self-aggregation is an important property of the assembly process, the steps involved in elastic fiber formation are not precisely known (5). Actually, it has been widely demonstrated that even short peptides and simple polymeric sequences belonging to elastin are able to give filaments with twisted-rope, hierarchical supramolecular organization similar to that found for the entire protein (6,7). Interestingly, Miao et al (8) have found that some mutated polypeptide sequences encoded by exons of human tropoelastin exhibit an ultrastructural organization different from the fibrils typical of elastin but rather similar to those found for amyloid networks, constituted by helical fibrils several microns long and about 10 nm wide (9).…”