Elastin amino acid repeating sequence

Coacervation occurs in tropoelastin solutions and is a precursor event in the assembly of elastin nanofibrils [42]. This phenomenon is thought to be mainly due to the interaction between hydro-phobic domains of tropoelastin. In scanning electron microscopy (SEM) picmres, nanofibril stmc-tures are visible in coacervate solutions of elastin-based peptides [37,43]. Indeed, Wright et al. [44] describe the self-association characteristics of multidomain proteins containing near-identical peptide repeat motifs. They suggest that this form of self-assembly occurs via specific intermolecular association, based on the repetition of identical or near-identical amino acid sequences. This specificity is consistent with the principle that ordered molecular assembhes are usually more stable than disordered ones, and with the idea that native-like interactions may be generally more favorable than nonnative ones in protein aggregates. 

Figure 1 Design of a crosslinkable amino acid sequence based on the elastin-mimetic repeat Lys-25.

Calcium in this case would coordinate with acyl oxygens from the polypeptide backbone of the protein, because of its unique amino acid sequences and potential conformations348). Non-polar peptides have been isolated from elastin which consists almost entirely of the three non-polar amino acids glycine, valine, and proline349). Portions of porcine tropoelastin have been partially sequenced350). Repeating tetra-, penta-, and hexapeptides have been observed. The tetrapeptide contains the sequence —Gly—Gly—L—Val—L—Pro— the pentapeptide —L—Val—L—Pro-... 

The other major protein in the extracellular matrix is elastin, which is the main component of elastic fibers found in ligaments, large arteries, and lungs. After synthesis and partial hydroxylation of proline residues, a 72 kDa molecule of tropoelastin is secreted into the matrix. This protein is rich in nonpolar amino acids and contains repeating sequences, such as (Val-Pro-Gly-Val-Gly). These sections form an amorphous, random-coiled structure with frequent reverse turns. Other recurrent sequences are rich in alanine with paired lysine residues, e.g., -Ala-Ala-Ala-Ala-Lys-Ala-Ala-Lys-... 

Amino acid sequences of specific tryptic peptides found in porcine tropoelastin. When tentative assignments are given, the designations are in parentheses. The common repeating units are underlined. In certain instances liberty was taken in defining a common repeating unit when there was only amino acid difference. These sequences are common to the extensible regions in elastin. The tetra, penta or hexa repeats appear to correspond to 15 to 25 percent of the total residues in the protein. The source for the sequence data is reference 1. 

Mature elastin is a linear polypeptide, tropoelastin, which has a molecular weight of about 72,000 and contains about 850 amino acid residues. Although glycine accounts for one third of the residues, the repeat sequence Gly-X-Y characteristic of collagen is not present in elastin. Instead, glycine residues are present in the repeat units Gly-Gly-Val-Pro, Pro-Gly-Val-Gly-Val, and Pro-Gly-Val-Gly-Val-Ala. Elastin is relatively rich in the nonpolar amino acids alanine, valine, and proline. In contrast to collagen, only a few hydroxyproline residues are present in elastin. Elastin contains no hydroxylysine or sugar residues. 

Figure 1 The amino acid sequence of SELP-47K The 884 amino acids have a molecular weight of 69,814 Da. It is composed of head and tail portions, and a series of silk-hke (GAGAGS) and elastin-hke (GVGVP) repeats (primary repetitive sequence in hold). Abbreviation key A=alanine D = aspartic acid E = glutamic acid ...

Elastin-like polypeptides (ELPs) are another class of synthetic biopolymers that consist of a repeating pentapeptide sequence that is represented in native elastin. The peptide sequence in ELPs is VPGXG, where X is any amino acid, except proline. ELPs are water soluble and can form micron- or sub-micron-sized aggregates moreover, they are biocompatible and nonimmunogenic, which in turn make it useful as a potent drug delivery system. ... 

Figure 3 (a) Comparison of the turbidimetric profiles for a series of chemosynthetic elastin polypeptides based on random copolymers of the repeat sequence [(Val-Pro-Gly-Val-Gly)i x(Val-Pro-Gly-Xaa-Gly)J, where fx refers to the mole fraction of variant pentapeptides within the polymer sequence. " (b) Hydrophobicity scale based on ft values for the copolymers described above as a function of guest residue identity and mole fraction, f. Note that hydrophobic amino acids shift the position of 7 toward lower temperature and that more polar guest residues shift the position of 7i toward higher temperatures in a manner commensurate with the level of substitution within the polypeptide sequence. Reprinted from Uriy, D. W. Gowda, D. C. Parker, T. M. etal. Biopolymers 99Z, 32(9), 1243 20(b) Copyright 1992, with permission from Wiley. 

Elastin is Cross-linked and Contains Repeating Sequences of Amino Acid Residues... 

The amino acid composition of elastin is similar to that of collagen with regard to glycine and hydroxyproline content, but hydroxylysine is absent. Repeating sequences of... 

Elastin-like polypeptides (ELPs) have been extensively studied due to the fact that they combine similar stimulus response properties to other artificial polymers such as poly(iV-isopropylacrylamide) (pNIPAM) with the advantages of a biologically derived material, that is, it is biocompatible, modular in its composition, and can be obtained by biological processes. ELPs are polypeptides that contain a short, repetitive peptide sequence, most commonly (VPGXG) that is derived from tropoelastin, the precursor of elastin. In this sequence, X represents any amino acid sequence except proline. Polypeptides composed of the pentapeptide repeat unit VPGXG possess a reversible lower critical solution temperature (LCST). Below the LCST, the peptide is soluble... 

Structural proteins such as collagen, elastin, and spider silk contain repeating sequences of amino acids. In 1983, Waite discovered that the protein secreted by the phenol gland of the blue sea mussel Mytilus edulis consists of closely related decapeptide and hexapeptide sequences with a combined molecular weight of approximately 130 kilodaltons (kDa).i He further elucidated that this protein is transformed into glue through enzymatic oxidation to form the adhesive plaques that anchor the mussel... 

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