Lozano G, Ninomiya Y, Thompson H, Olsen B R
Proc Natl Acad Sci U S A. 1985 Jun;82(12):4050-4. doi: 10.1073/pnas.82.12.4050.
Type IX collagen is a disulfide-bonded protein first isolated from hyaline cartilage. The structure of this collagen is unusual in that the molecules contain three triple-helical domains interspersed with noncollagenous regions. The molecules are heterotrimers composed of three genetically distinct polypeptide chains. In our laboratory, cDNAs specific for two of these polypeptide chains have recently been isolated. Here we report on the isolation of genomic clones by use of these cDNAs as probes for screening a chicken genomic library. Nucleotide sequence analysis of these clones shows that the exon structure of type IX collagen genes is fundamentally different from the exon structure of the genes for the fibrillar collagen types I-III. Whereas the sizes of exons in fibrillar collagen genes are related to a basic 54-base-pair coding unit, the exons of type IX collagen genes show a large variation in size and do not appear to be related to a 54-base-pair unit. We propose, therefore, that type IX collagen genes belong to a class of vertebrate collagen genes distinct from that of fibrillar collagens.
IX型胶原蛋白是一种首次从透明软骨中分离出来的二硫键结合蛋白。这种胶原蛋白的结构不同寻常，其分子包含三个穿插着非胶原蛋白区域的三股螺旋结构域。这些分子是由三条基因不同的多肽链组成的异源三聚体。在我们实验室，最近已分离出其中两条多肽链的特异性cDNA。在此，我们报道利用这些cDNA作为探针筛选鸡基因组文库从而分离基因组克隆的情况。对这些克隆的核苷酸序列分析表明，IX型胶原蛋白基因的外显子结构与I-III型纤维状胶原蛋白基因的外显子结构有根本差异。纤维状胶原蛋白基因中外显子的大小与一个基本的54碱基对编码单元相关，而IX型胶原蛋白基因的外显子大小差异很大，似乎与54碱基对单元无关。因此，我们提出IX型胶原蛋白基因属于一类与纤维状胶原蛋白基因不同的脊椎动物胶原蛋白基因。
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