A truncated laminin chain homologous to the B2 chain: structure, spatial expression, and chromosomal assignment.

作者：Pekka Kallunki, Kirsi Sainio, Roger L. Eddy, Mary Shannon Byers, Tuula Kallunki, Hannu V. Sariola, Konrad Beck, Heli Hirvonen, Thomas B. Shows, Karl Tryggvason · 发表于：The Journal of Cell Biology · 年份：1992 · DOI：10.1083/jcb.119.3.679 · 被引用次数：236 · 研究领域：Cell Adhesion Molecules Research、Wnt/β-catenin signaling in development and cancer、Skin and Cellular Biology Research

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 c...