INTRODUCTION
Elastin is the major extracellular matrix protein in tissues – such as the large arterial blood vessels, lung parenchyma, elastic ligaments, and skin – where it is accepted to be principally responsible for the physical properties of extensibility and elastic recoil which are particularly important for the function of these tissues. Elastin is also the major matrix protein in some cartilaginous tissues – such as ear cartilage – where the functional role of this protein is less evident.
Elastic fibres are made up of two major components: an elastin component and a microfibrillar component. The microfibrillar component, consisting of 10–12 nm filaments, is made up of at least five distinct proteins but thought to be predominantly composed of fibrillin, a 350 kDa protein which exists in two forms: fibrillin-1 and fibrillin-2 (Sakai et al., 1986; Zhang et al., 1994) (see also chapter 5 by Kielty et al., in this volume). The microfibrils also include two microfibril-associated glycoproteins (MAGP-1 and MAGP-2) (Gibson et al., 1991, 1996). Elastic fibres may also include a number of other components, including a 67 kDa chaperone protein known as the elastin binding protein (EBP) (Hinek et al., 1988; Hinek and Rabinovitch, 1994), and lysyl oxidase, the enzyme that catalyzes oxidative deamination of lysine residues in preparation for crosslink formation (Kagan and Trackman, 1991).