Fibronectin (FN1) binds many types of collagen, particularly when denatured (Ingham et al. 1985). A region of fibronectin known as the gelatin binding domain (GBD) is responsible for the interaction (Ingham et al. 1988); structures of this region bound to collagen alpha-1(I) are available (Erat et al. 2009, 2010). FN1 has been reported to bind isolated collagen alpha-1(I), alpha-2(I) and alpha-1(II) chains as well as several CNBr fragments (Ingham et al. 1988, 2002) indicating that there are multiple FN1 binding sites within each collagen chain (Dessau et al. 1978). FN1 conjugates can bind collagen types I through V (Bell & Engvall 1982), VII (Lapiere et al. 1994) and likely others. FN1 binds to aggregating collagen fibres, probably at the sites shown to bind denatured collagen, inhibiting the rate of collagen fibrillogenesis which may regulate the size of collagen fibres (Kleinman et al. 1981). Blocking the interaction of FN1 with collagen prevents collagen I fibril formation (McDonald et al. 1982). Newly assembled collagen fibrils colocalize with newly assembled FN1 fibrils (Li et al. 2003); FN1 fibril assembly and collagen fibril assembly may have common mechanistic elements (Kadler et al. 2008).