A rare amino acid found in elastin, formed by condensation of four molecules of lysine into a pyridinium ring.

'Elastin' is a highly elastic protein in connective tissue that allows many tissues in the body to resume their shape after stretching or contracting, such as the skin, lungs, and blood vessels.

2-(4-Amino-4-carboxybutyl)-1-(5-amino-5-carboxypentyl)-3,5-bis(3-amino-3-carboxypropyl)pyridinium. A rare amino acid found in elastin, formed by condensation of four molecules of lysine into a pyridinium ring.

Shiny, flexible bands of fibrous tissue connecting together articular extremities of bones. They are pliant, tough, and inextensile.

Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.