Durkin M E, Chakravarti S, Bartos B B, Liu S H, Friedman R L, Chung A E
Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260.
J Cell Biol. 1988 Dec;107(6 Pt 2):2749-56. doi: 10.1083/jcb.107.6.2749.
Entactin (nidogen), a 150-kD sulfated glycoprotein, is a major component of basement membranes and forms a highly stable noncovalent complex with laminin. The complete amino acid sequence of mouse entactin has been derived from sequencing of cDNA clones. The 5.9-kb cDNA contains a 3,735-bp open reading frame followed by a 3'-untranslated region of 2.2 kb. The open reading frame encodes a 1,245-residue polypeptide with an unglycosylated Mr of 136,500, a 28-residue signal peptide, two Asn-linked glycosylation sites, and two potential Ca2+-binding sites. Analysis of the deduced amino acid sequence predicts that the molecule consists of two globular domains of 70 and 36 kD separated by a cysteine-rich domain of 28 kD. The COOH-terminal globular domain shows homology to the EGF precursor and the low density lipoprotein receptor. Entactin contains six EGF-type cysteine-rich repeat units and one copy of a cysteine-repeat motif found in thyroglobulin. The Arg-Gly-Asp cell recognition sequence is present in one of the EGF-type repeats, and a synthetic peptide from the putative cell-binding site of entactin was found to promote the attachment of mouse mammary tumor cells.
巢蛋白（巢素）是一种150kD的硫酸化糖蛋白，是基底膜的主要成分，可与层粘连蛋白形成高度稳定的非共价复合物。小鼠巢蛋白的完整氨基酸序列已通过对cDNA克隆进行测序得出。5.9kb的cDNA包含一个3735bp的开放阅读框，后面跟着一个2.2kb的3'非翻译区。该开放阅读框编码一个1245个残基的多肽，其未糖基化的分子量为136500，有一个28个残基的信号肽、两个天冬酰胺连接的糖基化位点和两个潜在的Ca2+结合位点。对推导的氨基酸序列分析预测，该分子由两个分别为70kD和36kD的球状结构域组成，中间由一个28kD的富含半胱氨酸的结构域隔开。COOH末端球状结构域与表皮生长因子（EGF）前体和低密度脂蛋白受体具有同源性。巢蛋白包含六个EGF型富含半胱氨酸的重复单元和一个在甲状腺球蛋白中发现的半胱氨酸重复基序的拷贝。Arg-Gly-Asp细胞识别序列存在于其中一个EGF型重复序列中，并且发现来自巢蛋白假定细胞结合位点的合成肽可促进小鼠乳腺肿瘤细胞的附着。
