In molecular biology, the
type IV collagen C4 domain (or collagen IV NC1 domain) is a duplicated
domain present at the C-terminus of
type IV collagens. Each type IV collagen contains a long triple-helical collagenous domain flanked by a short 7S domain of 25
amino acids and a globular non-collagenous C4 domain of ~230 amino acids at the N and C terminus, respectively. In protomer assembly, the C4 domains of three chains interact, forming an C4 trimer, to select and register chains for
triple helix formation. In network assembly, the C4
trimers of two protomers interact, forming a C4 hexamer structure, to select and connect protomers.