Collagen type IV is specific for basement membranes (Probable). Together with fbl-1 and downstream of metalloprotease mig-17, recruits nidogen nid-1 to the gonad basement membrane thereby probably inducing basement membrane remodeling required for the directional migration of distal tip cells (PubMed:19104038). Required to restrict presynaptic growth at the neuromuscular junctions in late larval stage and in adult motor neurons (PubMed:25080592). Vital for embryonic development (PubMed:7691828, PubMed:8045258). 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. Exons 9 and 10 are mutually exclusive splicing exons. There is alternative usage of either exon 9 (isoform a) or exon 10 (isoform b). Localizes to the basement membrane between distal tip cells and the germline. Localizes to the intestinal basement membrane. Alternatively spliced, in part by RNA-binding protein asd-2, to produce isoforms which are expressed at different developmental stages (PubMed:18230701). Isoform a: Predominantly expressed in embryos (PubMed:7691828, PubMed:18230701). Isoform b: Predominantly expressed in larvae and adults (PubMed:7691828, PubMed:18230701). 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. Belongs to the type IV collagen family. Intron retention.