Sasaki M, Yamada Y
Laboratory of Developmental Biology and Anomalies, National Institute of Dental Research, Bethesda, Maryland 20892.
J Biol Chem. 1987 Dec 15;262(35):17111-7.
Laminin (Mr = 850,000) is a large basement membrane-specific glycoprotein composed of three chains: A, B1, and B2. Previously, we have reported the primary structure of the B1 chain of mouse laminin deduced from sequencing cDNA clones (Sasaki M., Kato, S., Kohno, K., Martin, G. R., and Yamada, Y. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 935-939). Here we report the isolation of overlapping cDNA clones spanning 7642 bases which encode the entire B2 chain. The nucleotide sequence of the clones contains an open reading frame of 4821 bases coding for a protein of 1607 amino acids including 33 amino acids of a presumptive signal peptide. The mRNA for the B2 chain contains 2.5 kilobases of 3'-untranslated region. The deduced amino acid sequence indicates that the B2 chain consists of six distinct domains, including two domains with alpha-helical, coiled-coil structures, two domains with cysteine-rich homologous repeats, and two globular domains. These structural features of the B2 chain are similar to those of the B1 chain. In addition, the amino acid sequences of the B2 and B1 chains demonstrate considerable homology, suggesting that the genes for these two chains arose from a common ancestor.
层粘连蛋白（分子量 = 850,000）是一种大型的基底膜特异性糖蛋白，由三条链组成：A链、B1链和B2链。此前，我们已报道从小鼠层粘连蛋白B1链的cDNA克隆测序推导得到的一级结构（佐佐木 M.、加藤 S.、 Kohno K.、马丁 G. R. 和山田 Y.（1987年）《美国国家科学院院刊》84, 935 - 939）。在此，我们报道了跨越7642个碱基的重叠cDNA克隆的分离，这些克隆编码整个B2链。这些克隆的核苷酸序列包含一个4821个碱基的开放阅读框，编码一个由1607个氨基酸组成的蛋白质，其中包括一个推定信号肽的33个氨基酸。B2链的mRNA含有2.5千碱基的3'非翻译区。推导得到的氨基酸序列表明，B2链由六个不同的结构域组成，包括两个具有α螺旋、卷曲螺旋结构的结构域，两个具有富含半胱氨酸同源重复序列的结构域，以及两个球状结构域。B2链的这些结构特征与B1链的相似。此外，B2链和B1链的氨基酸序列显示出相当高的同源性，表明这两条链的基因起源于一个共同的祖先。
