Collagen type XI has 3 alpha chain types. The alpha1(XI) and alpha2(XI) chains are distinct gene products unique to collagen XI, while alpha3(XI) is a hyperglycosylated form of the alpha1 chain for collagen II (Burgeson & Hollister 1979, Morris & Bächinger 1987). Collagen type XI is a fibril-forming collagen found in conjunction with collagens type II and IX in cartilage fibrils (Miller & Gay 1987, Mendler et al. 1989). It is thought to be the structural equivalent of collagen V in connective tissue collagen fibrils. The formation of cartilage collagen fibrils requires collagen XI, suggesting a regulatory function (Li et al. 1995, Wu and Eyre 1995).
Mutaions in COL11A1 result in fibrochondrogenesis, a severe, autosomal-recessive, short-limbed skeletal dysplasia (Tompson et al. 2010). Variations in COL11A1, COL11A2 and COL2A1 are associated with the inherited chondrodysplasias Marshall and Stickler syndromes (Annunen et al. 1999).
Collagen type XI is degraded by MMP1 (Eyre et al. 1984), MMP2 (Yu et al. 1990, Smith et al. 1991, Brown et al. 1996), MMP3 (Wu et al. 1991) and MMP9 (Hirose et al. 1992, Pormotabbed et al. 1994).