COL4A3 is a major structural component of basement membranes. It is composed of 3 alpha subunits, which are encoded by 6 different genes, alpha 1 through alpha 6. Each of these alpha subunits can form a triple helix structure with 2 other subunits to form COL4A3. Autoantibodies bind to the collagen molecules in the basement membranes of alveoli and glomeruli can cause goodpasture syndrome. COL4A3 is also linked to an autosomal recessive form of alport syndrome. COL4A3 is organized in a head-to-head conformation and each gene pair shares a common promoter.