Elastin's a protein in connective tissue that's elastic and allows many tissues in the body to resume their shape after stretching or contracting. Elastin helps skin to return to its original position when it's poked or pinched. Elastin's also an important load-bearing tissue in the bodies of mammals and used in places where mechanical energy's required to be stored. Composition Elastin's primarily composed of the amino acids glycine, valine, alanine, and proline. It's a specialized protein wit… (More on Elastin)