Hess J F, Casselman J T, FitzGerald P G
Department of Cell Biology and Human Anatomy, School of Medicine, University of California, Davis 95616.
Curr Eye Res. 1993 Jan;12(1):77-88. doi: 10.3109/02713689308999499.
Two proteins, with molecular weights of 49 (CP49) and 115 kDa (CP115) as judged by SDS PAGE, have been shown by immunocytochemistry to be components of the beaded filament, a cytoskeletal structure thus far demonstrated only in the lens fiber cell. We have used antibodies reactive with CP49 to screen a mouse lens cDNA expression library. An immunoreactive clone with an approximately 1.0 kb insert was identified and purified. DNA sequence analysis shows the presence of an open reading frame that extends from the upstream cloning site for 660 bases. Contained within this reading frame are 2 peptide sequences nearly identical to 2 peptide sequences obtained from purified bovine CP49. Northern analysis revealed that the mRNA for the CP49 is not detectable in mouse brain, muscle, lung, liver, or heart. A search of the Genbank database showed that the partial cDNA sequence for the murine CP49 is unique, but that this partial sequence shows a strong similarity to multiple members of the intermediate filament family, with greatest similarity to type I acidic cytokeratins. The data presented here suggests that the CP49 is related to, and possibly represents a new member of the intermediate filament family. These data, in concert with previously published work, suggests 1) the CP49 and CP115, which have been localized to the beaded filament, are related to the family of IF proteins, and 2) these two proteins comprise a cytoskeletal structure which is structurally distinct from classical 8-11 nm intermediate filaments, thus possibly comprising a structurally novel form of intermediate filament.
通过SDS-PAGE判断，有两种蛋白质，分子量分别为49 kDa（CP49）和115 kDa（CP115），免疫细胞化学显示它们是串珠状细丝的组成成分，串珠状细丝是一种迄今为止仅在晶状体纤维细胞中发现的细胞骨架结构。我们使用与CP49反应的抗体筛选了小鼠晶状体cDNA表达文库。鉴定并纯化了一个插入片段约为1.0 kb的免疫反应性克隆。DNA序列分析表明存在一个开放阅读框，从上游克隆位点延伸660个碱基。这个阅读框内包含2个肽序列，与从纯化的牛CP49获得的2个肽序列几乎相同。Northern分析显示，在小鼠脑、肌肉、肺、肝或心脏中检测不到CP49的mRNA。对Genbank数据库的搜索表明，小鼠CP49的部分cDNA序列是独特的，但该部分序列与中间丝家族的多个成员有很强的相似性，与I型酸性细胞角蛋白最为相似。本文提供的数据表明CP49与中间丝家族相关，可能代表该家族的一个新成员。这些数据与先前发表的研究结果一致，表明：1）定位于串珠状细丝的CP49和CP115与中间丝蛋白家族相关；2）这两种蛋白质构成一种细胞骨架结构，在结构上不同于经典的8-11 nm中间丝，因此可能构成一种结构新颖的中间丝形式。
