COMPLETE PRIMARY STRUCTURE OF THE HUMAN TYPE-IV COLLAGEN ALPHA-4(IV) CHAIN - COMPARISON WITH STRUCTURE AND EXPRESSION OF THE OTHER ALPHA(IV) CHAINS

The entire sequence of the human alpha 4(IV) collagen chain was determ ined from cDNA clones and polymerase chain reaction-amplified DNAs. Th e complete translation product has 1,690 amino acid residues and the p rocessed alpha 4(IV) chain proper 1,652 residues. There is a 38-residu e putative signal peptide, a 1,421-residue collagenous domain starting with a 23-residue noncollagenous sequence, and a 231-residue NC1 doma in. The Gly-Xaa-Yaa-repeat sequence of the collagenous domain is inter rupted at 26 locations by noncollagenous sequences of 1-12 residues in length. The alpha 4(IV) chain contains 31 cysteine residues of which 18 are conserved in the other type IV collagen alpha chains. The calcu lated molecular weight of the mature alpha 4(IV) chain is 164,123. Ana lysis of the primary structure showed that the alpha 4(IV) chain belon gs to the alpha 2-like type IV collagen chains together with alpha 2(I V) and alpha 6(IV). Northern analyses with RNA from several human feta l tissues revealed quite similar expression patterns for the alpha 4(I V) and alpha 3(IV) chains, but there were also distinct differences in some tissues. The expression patterns of alpha 5(IV) and alpha 6(IV) differed extensively between each other and they also differed from th ose of alpha 3(IV) and alpha 4(IV).