Hung M, rosenthal E, Boblett B, Benson S
Department of Biological Sciences, California State University, Hayward 94542, USA.
Exp Cell Res. 1995 Nov;221(1):221-30. doi: 10.1006/excr.1995.1370.
We have isolated and characterized the expression of a cDNA clone from the sea urchin Strongylocentrotus purpuratus that encodes a protein very similar to LBP/p40, originally identified as a nonintegrin, 67-kDa laminin binding protein. The deduced amino acid sequence of the protein, which we call spLBP/p40, shows significant similarity with the LBP/p40 from other sources, although significant divergence does occur at the carboxyl end. The S. purpuratus mRNA is present as a maternal transcript and its level remains constant until activation of zygotic transcription at the hatching blastula stage, whereupon the total spLBP/p40 increases through the pluteus larval stage. Adult tissues also contain the spLBP/p40 mRNA. Both maternal and zygotic transcripts are translated as determined by their presence in polysomes. Immunoblot analysis using an antibody raised against a recombinant fusion protein indicates that the concentration of the spLBP/p40 protein remains constant during development despite the postblastula increase in mRNA concentration. However, the spatial distribution of the protein changes from a uniform, intracellular distribution in all cells of cleavage and blastula stages to localized, elevated levels in cells of the gut, primary mesenchyme, and oral epithelium of prism larvae. The distribution of spLBP/p40 mRNA at different developmental stages, analyzed by in situ hybridization, reflects that of the protein. Our results argue against a laminin binding function for this protein; instead they place the spLBP/p40 gene in a class of previously described sea urchin genes involved in growth and proliferation.
我们从紫海胆（Strongylocentrotus purpuratus）中分离并鉴定了一个cDNA克隆的表达，该克隆编码一种与LBP/p40非常相似的蛋白质，LBP/p40最初被鉴定为一种非整合素的67 kDa层粘连蛋白结合蛋白。我们将该蛋白质推导的氨基酸序列称为spLBP/p40，它与其他来源的LBP/p40显示出显著的相似性，尽管在羧基末端确实存在显著差异。紫海胆的mRNA以母源转录本的形式存在，其水平在合子转录在孵化囊胚阶段激活之前保持恒定，随后在长腕幼虫阶段spLBP/p40的总量增加。成体组织中也含有spLBP/p40 mRNA。母源和合子转录本均在多核糖体中翻译，这由它们在多核糖体中的存在所确定。使用针对重组融合蛋白产生的抗体进行的免疫印迹分析表明，尽管囊胚后期mRNA浓度增加，但spLBP/p40蛋白的浓度在发育过程中保持恒定。然而，该蛋白的空间分布从卵裂期和囊胚期所有细胞中的均匀细胞内分布，变为棱柱幼虫肠道、初级间充质和口上皮细胞中的局部升高水平。通过原位杂交分析不同发育阶段spLBP/p40 mRNA的分布，反映了该蛋白的分布情况。我们的结果表明该蛋白不具有层粘连蛋白结合功能；相反，它们将spLBP/p40基因归为一类先前描述的参与生长和增殖的海胆基因。
