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Collagen IV (Alpha 3)
Collagen IV (Alpha 3),encoded by the human COL4A3 gene, is a subunit of type IV collagen, the major structural component of basement membranes. In Goodpasture syndrome, autoantibodies bind to collagen in the basement membranes of alveoli and glomeruli. The epitopes that elicit these autoantibodies are localized to the non-collagenous C-terminal domain of this protein. There are 6 alternate transcripts unique to this gene and alternate splicing is restricted to the 6 exons encoding this domain. This protein is widely expressed. Two protein isoforms (1 and 2/Delta26/GPBPD26) are produced by alternative splicing. This gene is also linked to the autosomal recessive Alport syndrome. The mutations contributing to this syndrome are also located within the exons encoding this C-terminal region. This protein phosphorylates the Goodpasture autoantigen in vitro on Ser and Thr residues. Isoform 2 seems less active. (From LocusLink, Swiss-Prot and NCI) (NCI Thesaurus)