AMINO-ACID-SEQUENCE AND GENE ORGANIZATION OF CYTOKERATIN NO-19, AN EXCEPTIONAL TAIL-LESS INTERMEDIATE FILAMENT PROTEIN
AMINO-ACID-SEQUENCE AND GENE ORGANIZATION OF CYTOKERATIN NO-19, AN EXCEPTIONAL TAIL-LESS INTERMEDIATE FILAMENT PROTEIN
复制标题
DOI：
10.1002/j.1460-2075.1986.tb04438.x
复制
发表时间：
1986-08-01
期刊：
影响因子：
11.4
通讯作者：
FRANKE, WW
中科院分区：
文献类型：
--
作者：
BADER, BL;MAGIN, TM;FRANKE, WW
我们从牛膀胱尿路上皮文库中分离出一个cDNA克隆，它编码已知最小的中间丝（IF）蛋白，即此前被认为分子量为40000的简单上皮细胞角蛋白（相当于人细胞角蛋白19）。然后利用这个克隆分离出相应的基因，我们确定了其完整的核苷酸序列，并推导出所编码蛋白质的氨基酸序列。这种由399个氨基酸组成（分子量43893）的细胞角蛋白被鉴定为一种典型的酸性（I型）细胞角蛋白，但与所有其他中间丝蛋白不同的是，它没有羧基末端的非α-螺旋尾结构域。相反，它在α-螺旋杆状结构上有一个13个氨基酸的延伸。编码细胞角蛋白19的基因也很特殊。它仅含有5个内含子，其位置与其他中间丝蛋白基因的内含子位置相对应。然而，在所有其他中间丝蛋白中划分对应于从α-螺旋杆状结构到非α-螺旋尾结构转变区域的一个内含子在细胞角蛋白19基因中缺失。通过对纯化的细胞角蛋白19进行体外重组，我们发现它像其他I型细胞角蛋白一样，在没有II型细胞角蛋白伴侣的情况下，不会形成典型的中间丝。相反，它形成直径为10 - 11nm、长度为40 - 90nm的杆状结构，这似乎代表了一些细胞角蛋白分子的侧向关联。我们的研究结果表明，非α-螺旋尾结构域不是中间丝蛋白必不可少的特征。这种蛋白质的基因结构为蛋白质构象变化与外显子边界的相关性提供了一个显著的案例。
We have isolated a cDNA clone from a bovine bladder urothelium library which encodes the smallest intermediate filament (IF) protein known, i.e. the simple epithelial cytokeratin (equivalent to human cytokeratin 19) previously thought to have mol. wt 40000. This clone was then used to isolate the corresponding gene from which we have determined the complete nucleotide sequence and deduced the amino acid sequence of the encoded protein. This cytokeratin of 399 amino acids (mol. wt 43 893) is identified as a typical acidic (type I) cytokeratin but differs from all other IF proteins in that it does not show the carboxyterminal, non-.alpha.-helical tail domain. Instead it contains a 13 amino acids extension of the .alpha.-helical rod. The gene encoding cytokeratin 19 is also exceptional. It contains only five introns which occur in positions corresponding to intron positions in other IF protein genes. However, an intron which in all other IF proteins demarcates the region corresponding to the transition from the .alpha.-helical rod into the non-.alpha.-helical tail is missing in the cytokeratin 19 gene. Using in vitro reconstitution of purified cytokeratin 19 we show that it reacts like other type I cytokeratins in that it does not form, in the absence of a type II cytokeratin partner, typical IF. Instead it forms 40-90 nm rods of 10-11 nm diameter which appear to represent lateral associations of a number of cytokeratin molecules. Our results demonstrate that the non-.alpha.-helical tail domain is not an indispensable feature of IF proteins. The gene structure of this protein provides a remarkable case of a correlation of a change in protein conformation with an exon boundary.