Abstract
The human COL11A2 gene was analyzed from two overlapping cosmid clones that were previously isolated in the course of searching the human major histocompatibility region (Janatipour, M., Naumov, Y., Ando, A., Sugimura, K., Okamoto, N., Tsuji, K., Abe, K., and Inoko, H. (1992) Immunogenetics 35, 272-278). Nucleotide sequencing defined over 28,000 base pairs of the gene. It was shown to contain 66 exons. As with most genes for fibrillar collagens, the first intron was among the largest, and the introns at the 5'-end of the gene were in general larger than the introns at the 3'-end. Analysis of the exons coding for the major triple helical domain indicated that the gene structure had not evolved with the genes for the major fibrillar collagens in that there were marked differences in the number of exons, the exon sizes, and codon usage. The gene was located close to the gene for the retinoic X receptor beta in a head-to-tail arrangement similar to that previously seen with the two mouse genes (P. Vandenberg and D. J. Prockop, submitted for publication). Also, there was marked interspecies homology in the intergenic sequences. The amino acid sequences and the pattern of charged amino acids in the major triple helix of the alpha 2(XI) chain suggested that the chain can be incorporated into the same molecule as alpha 1(XI) and alpha 1(V) chains but not into the same molecule as the alpha 3(XI)/alpha 1(II) chain. The structure of the carboxyl-terminal propeptide was similar to the carboxyl-terminal propeptides of the pro alpha 1(XI) chain and pro alpha chains of other fibrillar collagens, but it was shorter because of internal deletions of about 30 amino acids.
Highlights
Over 19 types of collagens are known, each with an apparently unique biological function [1,2,3]
Initial analyses of the genes for the major fibrillar collagens revealed a striking pattern in the exons encoding for the major triple helical domains of the proteins
The results suggested that the genes for the fibrillar collagens evolved from a 54-bp exon that was duplicated during evolution
Summary
Over 19 types of collagens are known, each with an apparently unique biological function [1,2,3]. During the maturation of articular cartilage, isolated fractions rich in type XI collagen were found to contain an increasing proportion of the ␣1(V) chain and a decreasing proportion of ␣1(XI) chains [7]. These observations and others [13,14,15,16,17] led to the suggestion [2] that type V and type XI collagens are a heterogeneous class of collagens comprised of five or six different ␣ chains, i.e. the ␣1(V), ␣2(V), ␣3(V), ␣1(XI), and ␣2(XI) together with the ␣3(XI) chain, which apparently has the same primary structure as the ␣1(II) chain. The results demonstrate that (a) the gene structure did not evolve with the genes for the major fibrillar collagens in that there were marked differences in the number of exons, the exon sizes, and the codon usage [1, 3]; (b) the gene was located close to the gene for the retinoic X receptor  in a head-to-tail arrangement similar to that seen previously with the two mouse genes, and there was marked interspecies homology in the intergenic sequences; (c) the amino acid sequences and the pattern of charged amino acids in the major triple helix of both the ␣1(XI) chain [11] and ␣2(XI) chain [18, 19] as well as the ␣1(V) chain [20] differed from the charged amino acid pattern seen with the ␣3(XI)/␣1(II) chain [21], an observation suggesting that the ␣3(XI)/␣1(II) chain is not incorporated into the same molecule; and (d) the structure of the C-propeptide was similar to the C-propeptides of the pro␣1(XI) chain and pro␣ chains of other fibrillar collagens, but it was shorter because of internal deletions of about 30 amino acids
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