Merck, C5533-5MG, Collagen from human placenta

All collagen molecules are composed of three polypeptide chains arranged in a triple helical conformation, with a primary structure that is mostly a repeating motif with glycine in every third position and proline or 4-hydroxyproline frequently preceding the glycine residue. Type IV collagen occurs only in the basement membranes and contains up to six genetically distinct a-chains. Type IV collagens are localized to the basement membrane and they are network-forming proteins. It is encoded by six different genes: collagen type IV α1 (COL4A1), COL4A2, COL4A3, COL4A4, COL4A5 and COL4A6. Both COL4A1 and COL4A2 genes are mapped to human chromosome 13q34. The proteins encoded by the two genes share 45% homology. They contain: a non-collagenous (NC1) domain, triple-helical collagenous domain and Gly-Xaa-Yaa repeats in common. Both COL4A3 and COL4A4 genes are located on human chromosome 2q36.3. In tissues, type IV collagens are present as procollagens.