The Amino Acid Sequence Coded by the Rarely Expressed Exon 26A of Human Elastin Contains a Stable β-Turn with Chemotactic Activity for Monocytes

Abstract

The structural and biological properties of the amino acid sequence coded by the rarely expressed exon 26A of human elastin were investigated. The C-terminal portion of this sequence, corresponding to residues 600-619 of human tropoelastin, REGDPSSSQHLPSTPSSPRV and three shorter derived peptides, LREGDPSS, SSSQHLPS, and LPSTPSSP, were synthesized and studied. Spectroscopic analyses by CD and NMR have identified a type II beta-turn within the sequence REGD of the octapeptide LREGDPSS. This structural motif was found also in the tetrapeptide REGD in both trifluoroethanol and water. The CD spectrum of the tetrapeptide REGD in trifluoroethanol was consistent with a pure type II beta-turn. A high chemotactic activity for monocytes was exhibited by the structured peptides REGD (CI 0.90 at 10(-)7 M) and LREGDPSS (CI 0.80 at 10(-)11 M), at variance with the unfolded peptides LPSTPSSP and SSSQHLPS, suggesting that this activity is strictly correlated with folded structures. Because the exon 26A of human elastin is expressed in the neointima of hypertensive pulmonary arteries, and macrophages are present in this pathologic tissue [Liptay et al. (1993) J. Clin. Invest. 91, 588-594], the chemotactic activity for human monocytes reported in this paper is consistent with an active role played by the exon 26A in inducing the migration of the monocyte/macrophage cells to the neointima.

Glycosaminoglycans Mediate the Coacervation of Human Tropoelastin through Dominant Charge Interactions Involving Lysine Side Chains

“…Our data demonstrate that 26A is essentially random coil or highly flexible in aqueous solution. Apart from a reported type II ␤ turn with a 4-amino acid portion in high concentrations of trifluoroethanol, this is consistent with the observations of Bisaccia et al (27). There appears to be greater heparin binding by GST26A than GST, suggesting a contribution by 26A to GAG association (data not shown) that might be relevant in the elastic fiber after elastogenesis.…”

“…19) in tropoelastin and consequently for its physiological significance. This region alters lysyl oxidase reactivity on tropoelastin containing the sequence (26), and isolated 26A displays chemotactic activity for monocytes (27). While 26A is evident in human cDNA, homologous counterparts have yet to be identified in other animals.…”

Domain 26 of Tropoelastin Plays a Dominant Role in Association by Coacervation

“…Coacervation of SHEL26C did not occur at temperatures below ϳ45°C. Temperatures for SHEL26C were at least 10°C higher than those required to reach the same extent using SHEL26(⌬26A)C, even though the concentration of SHEL26C used in the assay was higher than SHEL26(⌬26A)C. Domain 26A is a hydrophilic domain unique to human tropoelastin and is largely unstructured except for a single ␤-turn formed around the sequence REGD (22). Its effect on coacervation would be more obvious in the shorter fragments of tropoelastin studied here than in the full-length isoforms because it constitutes a larger proportion of the smaller molecule.…”

Elastin structure and its involvement in skin photoageing

“…When inserted into the final transcript, exon 26A produces an increase of 99 base pairs, which code for 33 amino acids (GADEGVRRSLSPELREGDPSSSQHLPSTPSSPR) in the tropoelastin protein sequence (Fig. 3) and alter its structural and biological properties [37,64,65]. Figure 2 Changes in elastic fibre organization with skin photoageing.…”