Type IV collagen is the major structural component of glomerular basement membranes (GBM), forming a 'chicken-wire' meshwork together with laminins, proteoglycans and entactin/nidogen. Arresten, comprising the C-terminal NC1 domain, inhibits angiogenesis and tumor formation. The C-terminal half is found to possess the anti-angiogenic activity. Specifically inhibits endothelial cell proliferation, migration and tube formation. There are six type IV collagen isoforms, alpha 1(IV)-alpha 6(IV), each of which can form a triple helix structure with 2 other chains to generate type IV collagen network. Interacts with EFEMP2 (By similarity). Highly expressed in placenta. Alpha chains of type IV collagen have a non-collagenous domain (NC1) at their C-terminus, frequent interruptions of the G-X-Y repeats in the long central triple-helical domain (which may cause flexibility in the triple helix), and a short N-terminal triple-helical 7S domain. NC1 domain mediates hexamerization of alpha chains of type IV collagen (By similarity). Lysines at the third position of the tripeptide repeating unit (G-X-Y) are hydroxylated. The modified lysines can be O-glycosylated. Contains 4-hydroxyproline (Probable). Prolines at the third position of the tripeptide repeating unit (G-X-Y) are hydroxylated in some or all of the chains (By similarity). Contains 3-hydroxyproline. This modification occurs on the first proline residue in the sequence motif Gly-Pro-Hyp, where Hyp is 4-hydroxyproline. Type IV collagens contain numerous cysteine residues which are involved in inter- and intramolecular disulfide bonding (PubMed:2844531). 12 of these, located in the NC1 domain, are conserved in all known type IV collagens. The trimeric structure of the NC1 domains is stabilized by covalent bonds (sulfilimine cross-links) between Lys and Met residues (PubMed:12011424). These cross-links are important for the mechanical stability of the basement membrane (By similarity). Sulfilimine cross-link is catalyzed by PXDN (By similarity). Proteolytic processing produces the C-terminal NC1 peptide, arresten. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Disease susceptibility is associated with variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Causative mutations affect a binding site for miR-29 microRNA located within the 3'UTR of COL4A1 and lead to an up-regulation of this gene. Belongs to the type IV collagen family. Was shown to inhibit expression of hypoxia-inducible factor 1alpha and ERK1/2 and p38 MAPK activation, and to function as a ligand for alpha1/beta1 integrin. However, this study was later retracted.