The composition of the extracellular matrix of all vertebrates is dominated by a class of molecules known as collagens, each with a unique feature suited to its function and location. Type IV collagen is a major constituent of basement membranes. This molecule is a continuous triple helix, about 400 nm in length, composed of at least two different α chain subunits termed α1 (IV) and α2 (IV) which may be composed of the same or different molecules. Upon proteolysis, fragments of 125 kDa, 95 kDa, and 60 kDa are released from a parent α1 (IV) chain, whereas fragments of 115 kDa, 80 kDa, and 45 kDa apparently originate from a distinct α2 (IV) chain.
Collagens are known to have multiple functions. They are involved in tissue differentiation, morphogenesis and repair; play a role in the maintenance of tissue architecture; and form the filtration barrier of blood vessels.
