Collagen type IV is specific for basement membranes (Probable). Required to restrict presynaptic growth at the neuromuscular junctions (NMJ) in late larval stage and in adult motor neurons (PubMed:25080592). May play a role in axon regeneration in embryos following injury in D-type motor neurons (PubMed:27984580). Trimers of two alpha 1(IV) and one alpha 2(IV) chain. Type IV collagen forms a mesh-like network linked through intermolecular interactions between 7S domains and between NC1 domains. 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. Prolines at the third position of the tripeptide repeating unit (G-X-Y) are hydroxylated in some or all of the chains. Type IV collagens contain numerous cysteine residues which are involved in inter- and intramolecular disulfide bonding. 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 between Lys and Met residues. At 20 degrees Celsius, there is reduced axon regeneration following injury in D-type motor neurons in temperature-sensitive mutant embryos. Belongs to the type IV collagen family.