The collagen family

Abstract

Collagens are the most abundant proteins in mammals. The collagen family comprises 28 members that contain at least one triple-helical domain. Collagens are deposited in the extracellular matrix where most of them form supramolecular assemblies. Four collagens are type II membrane proteins that also exist in a soluble form released from the cell surface by shedding. Collagens play structural roles and contribute to mechanical properties, organization, and shape of tissues. They interact with cells via several receptor families and regulate their proliferation, migration, and differentiation. Some collagens have a restricted tissue distribution and hence specific biological functions.

Figure 1.

Structural organization of collagens. Domain composition and supramolecular assemblies of collagens. COL, Collagenous, triple-helical, domains; NC, Non-collagenous, nontriple-helical, domains. They are numbered from the carboxy- to the amino-terminus, except for collagen VII. (Figure continued on following page.)

Figure 1.

Structural organization of collagens. Domain composition and supramolecular assemblies of collagens. COL, Collagenous, triple-helical, domains; NC, Non-collagenous, nontriple-helical, domains. They are numbered from the carboxy- to the amino-terminus, except for collagen VII. (Figure continued on following page.)

Figure 2.

Supramolecular assemblies formed by collagens.

Figure 3.

Collagen cross-links. Lysyl-mediated mature cross-links: argoline, deoxypyridinoline, pyridinoline, and histidinohydroxylysinonorleucine. Advanced glycation endproducts: glucosepane and pentosidine.