Solid-State NMR Studies of Elastin and Elastin Peptides

The skin and blood vessels of a vertebrate have a uniquely resilient and elastic quality to them. These properties are traced to elastin, the principal protein component of the fibers that comprise a large portion of these elastic tissues. Numerous reviews have been written on the biology and chemistry of this unique protein [1–3]. Briefly, the elastin gene encodes tropoelastin, which is crosslinked in post-translational modification to form insoluble elastin or, simply, elastin. The molecular weight of tropoelastin is large, with molecular weights ranging from 70 to 80 kDa, and its high-resolution structure is not yet solved. Generally, tropoelastin and insoluble elastin are considered to have two “domains,” namely, hydrophobic and crosslinking. Much attention has been focused on the hydrophobic regions that are dominated with the small nonpolar amino acids, glycine, alanine, proline, and valine. A number of repeating polypeptide sequences are found in this domain. Among them are (VPGVG) _n and (PGVGVA) _n . The crosslinking domain is rich with alanines, with a typical repeat sequence of (KAAK) _n or (KAAAK) _n . In portions of tropoelastin, the hydrophobic and crosslinking domains alternate. Figure 1 illustrates several domains of rat tropoelastin, as reported by Pierce et al. [4].