Corpuz L M, Funderburgh J L, Funderburgh M L, Bottomley G S, Prakash S, Conrad G W
Division of Biology, Kansas State University, Manhattan 66506-4901, USA.
J Biol Chem. 1996 Apr 19;271(16):9759-63. doi: 10.1074/jbc.271.16.9759.
Previous studies showed that the keratan sulfate-containing proteoglycans of bovine corneal stroma contain three unique core proteins designated 37A, 37B, and 25 (Funderburgh, J. L., Funderburgh, M. L., Mann, M. M., and Conrad, G. W. (1991) J. Biol. Chem. 266, 14226-14231). Degenerate oligonucleotides designed from amino acid sequences of the 37A protein were used to screen a cDNA expression library from cultured bovine keratocytes. A cDNA clone coding for keratocan, a 37A protein, was isolated and sequenced. The deduced keratocan amino acid sequence is unique but related to two other keratan sulfate-containing proteins, lumican (the 37B core protein) and fibromodulin. These three proteins share approximately 35% amino acid identity and a number of conserved structural features. Northern hybridization and immunoblotting of tissue extracts found keratocan distribution to be more limited than that of lumican or fibromodulin. Keratocan is abundant in cornea and sclera and detected in much lesser amounts in skin, ligament, cartilage, artery, and striated muscles. Only in cornea was keratocan found to contain large, sulfated keratan sulfate chains. Keratocan, like lumican, is a core protein of a major corneal proteoglycan but is present in non-corneal tissues primarily as a nonsulfated glycoprotein.
先前的研究表明，牛角膜基质中含硫酸角质素的蛋白聚糖含有三种独特的核心蛋白，分别命名为37A、37B和25（芬德伯格，J.L.，芬德伯格，M.L.，曼，M.M.，和康拉德，G.W.（1991年）《生物化学杂志》266，14226 - 14231）。根据37A蛋白的氨基酸序列设计的简并寡核苷酸用于筛选培养的牛角膜细胞的cDNA表达文库。分离并测序了一个编码角膜蛋白聚糖（一种37A蛋白）的cDNA克隆。推导的角膜蛋白聚糖氨基酸序列是独特的，但与另外两种含硫酸角质素的蛋白，即光蛋白聚糖（37B核心蛋白）和纤调蛋白相关。这三种蛋白共享约35%的氨基酸同一性以及一些保守的结构特征。对组织提取物进行的Northern杂交和免疫印迹发现，角膜蛋白聚糖的分布比光蛋白聚糖或纤调蛋白更有限。角膜蛋白聚糖在角膜和巩膜中含量丰富，在皮肤、韧带、软骨、动脉和横纹肌中的含量则少得多。仅在角膜中发现角膜蛋白聚糖含有大的、硫酸化的硫酸角质素链。角膜蛋白聚糖与光蛋白聚糖一样，是主要角膜蛋白聚糖的核心蛋白，但在非角膜组织中主要以非硫酸化糖蛋白的形式存在。
