is a type of collagen
found primarily in the basal lamina
. The C-terminus domain 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
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.
There are six human genes associated with it:
Mutations to the genes coding for type-IV collagen lead to Alport syndrome.