Structure of cDNA clones coding for human type II procollagen. The α1(II) chain is more similar to the α1(I) chain than two other α chains of fibrillar collagens

Abstract

Overlapping cDNA clones were isolated for human type II procollagen. Nucleotide sequencing of the clones provided over 2.5 kb of new coding sequences for the human proα1(II) gene and the first complete amino acid sequence of type II procollagen from any species. Comparison with published data for cDNA clones covering the entire lengths of the human type I and type III procollagens made it possible to compare in detail the coding sequences and primary structures of the three most abundant human fibrillar collagens. The results indicated that the marked preference in the third base codons for glycine, proline and alanine previously seen in other fibrillar collagens was maintained in type II procollagen. The domains of the proα1(II) chain are about the same size as the same domains of the proα chains of type I and type III procollagens. However, the major triple-helical domain is 15 amino acid residues less than the triple-helical domain of type III procollagen. Comparison of hydropathy profiles indicated that the α chain domain of type II procollagen is more similar to the α chain domain of the proα1(I) chain than to the proα2(I) chain or the proα1(III) chain. The results therefore suggest that selective pressure in the evolution of the proα1(II) and proα1(I) genes is more similar than the selective pressure in the evolution of the proα2(I) and proα1(III) genes.