A truncated laminin chain homologous to the B2 chain: structure, spatial expression, and chromosomal assignment.
A truncated laminin chain homologous to the B2 chain: structure, spatial expression, and chromosomal assignment.
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DOI：
10.1083/jcb.119.3.679
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发表时间：
1992-11
期刊：
影响因子：
--
通讯作者：
Tryggvason K
中科院分区：
文献类型：
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作者：
Kallunki P;Sainio K;Eddy R;Byers M;Kallunki T;Sariola H;Beck K;Hirvonen H;Shows TB;Tryggvason K
我们描述了一种新的层粘连蛋白链的鉴定。从人纤维肉瘤HT1080细胞全长5200bp的文库中分离到重叠克隆。第二组克隆包含一个可选的3‘端序列，总长度为4,316个核苷酸。较长的序列包含1,193个残基的多肽的开放阅读框架。在编码1,111个残基的多肽的羧基末端缩短了替代序列。该氨基酸序列包含21个氨基酸的推定信号肽和1,172个残基或1,090个残基，具有5个不同的结构域，与层粘连蛋白链中的I-V结构域同源。氨基酸序列比较表明，新的层粘连蛋白链与层粘连蛋白B2链具有同源性。然而，这里分离的新的层粘连蛋白链的结构与B2链的结构显著不同，因为它没有结构域VI，并且结构域V、IV和III更短，导致层粘连蛋白链被截断。该替代序列具有缩短的结构域I/II。根据目前的命名法，这里描述的链被命名为B2t。计算了层粘连蛋白与B2t链结构域I/II可能的链相互作用，表明在某些层粘连蛋白分子中，B2t链可以取代B2链。层粘连蛋白B2t链基因(LAMB2T)位于染色体1q25-Q31上，与层粘连蛋白B2链基因非常接近。Northern分析表明，B2t链在几个人胎儿组织中都有表达，但与层粘连蛋白B1和B2链不同。通过原位杂交，B2T链的表达定位于皮肤、肺和肾脏的特定上皮细胞，而不是层粘连蛋白B2链在相同组织中的一般上皮细胞和内皮细胞的表达。
We describe the identification of a novel laminin chain. Overlapping clones were isolated from a human fibrosarcoma HT1080 cell cDNA library spanning a total of 5,200 bp. A second set of clones contained an alternative 3' end sequence giving a total of 4,316 bp. The longer sequence contained an open reading frame for a 1,193-residue-long polypeptide. The alternative sequence was shortened at the carboxyl- terminal end coding for a 1,111-residue-long polypeptide. The amino acid sequence contained 21 amino acids of a putative signal peptide and 1,172 residues or alternatively 1,090 residues of a sequence with five distinct domains homologous to domains I-V in laminin chains. Comparison of the amino acid sequences showed that the novel laminin chain is homologous to the laminin B2 chain. However, the structure of the novel laminin chain isolated here differs significantly from that of the B2 chain in that it has no domain VI and domains V, IV, and III are shorter, resulting in a truncated laminin chain. The alternative sequence had a shortened domain I/II. In accordance with the current nomenclature, the chain characterized here is termed B2t. Calculation of possible chain interactions of laminin chains with the B2t chain domain I/II indicated that the B2t chain can replace the B2 chain in some laminin molecules. The gene for the laminin B2t chain (LAMB2T) was localized to chromosome 1q25-q31 in close proximity to the laminin B2 chain gene. Northern analysis showed that the B2t chain is expressed in several human fetal tissues but differently from the laminin B1 and B2 chains. By in situ hybridization expression of the B2t chain was localized to specific epithelial cells in skin, lung, and kidney as opposed to a general epithelial and endothelial cell expression of the laminin B2 chain in the same tissues.