FC0022
Elastin  -  Elastin

Biological function
The elastic fiber formed by the self-assembly (coacervation) of tropoelastin monomers. Its essential functional property, the ability to contract reversibility after stretching.

Domain organization/sequence features
Contains (VPGVG) repeats.

Structural evidence
Solid-state NMR provides evidence for a high degree of dynamic disorder within the fibrils, with random-coil-like secondary chemical shift values of all backbone carbon atoms. Tightly bound waters are absent in both dry and hydrated elastin and (ii) that the backbone in the hydrated protein is highly disordered with large amplitude motions. Comparison of the observed shifts with accepted values for α-helices, β -sheets, or random coils indicates a random coil structure at all carbons.

Structure/Mechanism
Coacervation in this case is driven by a distributed array of hydrophobic interactions and a few water-mediated hydrogen bonded interactions. The backbone disorder is a consequence of a high-proline content.

Mechanism category
flexibility/entropy modulation

Significance
(1) A fundamental requirement for elastomeric domains is to remain disordered, even when aggregated; (2) disorder is an indirect consequence of the inability of the polypeptide to form a compact, water-excluding core involving extensive backbone self-interactions; (3) most significantly, the fact that a minimum threshold of combined P, G content appears to be fulfilled by proteins forming such diverse biomaterials as human aorta, spider silk, and lizard egg shells suggests that maintaining a critical level of disorder is not only a fundamental requirement but may very well constitute the single most essential design principle of self-assembling elastic proteins.

Further reading
17098192