Structural comparison of the chicken genes for alpha 1(VI) and alpha 2(VI) collagen

The chicken alpha 1(VI) polypeptide is encoded by a single gene spanning 21 kbp of genomic DNA. This gene is composed of 34 exons and 33 introns. Its structure is closely related to that of the alpha 2(VI) collagen gene, suggesting that the two genes evolved by gene duplication. Both genes contain 19 exons coding for the triple-helical domain. These exons are multiples of 9 bp (27, 36, 45, 54, 63 and 90 bp) and encode an integral number of collagenous Gly-Xaa-Yaa triplets. Since there is no convincing correlation to a building block of 54 bp, it is unlikely that type VI collagen has evolved from a primordial 54-bp module as suggested for all fibrillar collagens.