Type-IV collagen

Type-IV collagen is a type of collagen found primarily in the basal lamina. The type IV collagen C4 domain at the C-terminus is not removed in post-translational processing, and the fibers link head-to-head, rather than in parallel. Also, type-IV lacks the regular glycine in every third residue necessary for the tight, collagen helix. This makes the overall arrangement more sloppy with kinks. These two features cause the collagen to form in a sheet, the form of the basal lamina

There are six human genes associated with it:
 * COL4A1, COL4A2, COL4A3, COL4A4, COL4A5, COL4A6

Clinical significance
The alpha 3 protein constituent of type-IV collagen is thought to be the antigen implicated in Goodpasture's syndrome, wherein the immune system attacks the basement membranes of the glomeruli and the alveoli.

Mutations to the genes coding for type-IV collagen lead to Alport syndrome.