Collagen IV is the major component of basement membranes. The human a3 chain of collagen IV contains an antigenic domain called Goodpasture antigen, ubicated in the non collagenous carboxyl-terminal region of the molecule (NC1), that is the target for the circulating immunopathogenic antibodies present in patients with Goodpasture syndrome. The gene region encoding the Goodpasture antigen generates multiple alternative products that retain the antigen amino-terminal region with a five residue motif (KRGDS). This motif is exclusive to the human alpha 3(IV) chain. The serine therein is the major in vitro cAMP-dependent protein kinase phosphorylation site in the isolated antigen and includes the RGD cell adhesion site. It has been postulated that its phosphorylation might play a role in pathogenesis and influence cell attachment to basement membrane. The folding of the NC 1 domain is determined by six disulfide bridges and is essential for Goodpasture antibodies binding and phosphorylation. We propose to produce recombinant natively folded Goodpasture antigen and its splice variants in eukaryotic cells in order to study its cell-adhesive properties and the role that specific phosphorylation and alternative splicing play in it.