Sakai N, Mori S, Izumi S, Haino-Fukushima K, Ogura T, Maekawa H, Tomino S
Department of Biology, Tokyo Metropolitan University, Japan.
Biochim Biophys Acta. 1988 Feb 28;949(2):224-32. doi: 10.1016/0167-4781(88)90086-3.
A group of structurally related proteins, referred to as '30K proteins', accumulate in a stage-dependent fashion in the larval hemolymph of the silkworm, Bombyx mori. To investigate the regulatory mechanisms of the 30K protein biosynthesis in the fat body, mRNA sequences coding for these plasma proteins were cloned and their structures and expression during the larval development were studied. Five plasmid clones, each bearing a distinct mRNA sequence coding for the 30K protein component, were isolated from a cDNA library constructed from the fat body poly(A)RNA of the mid-fifth instar larvae. These clones were remarkably similar to each other with respect to both the nucleotide and the amino-acid sequences. Each clone carried an open reading frame for amino-acid residues 251 to 264, with a typical signal sequence for transmembrane secretion at the deduced amino-terminal domain. Northern blot hybridization provided evidence that the developmental change in the amount of 30K protein mRNAs in the fat body reflects well that of the hemolymph concentration of 30K proteins, indicating that the biosynthesis of 30K proteins is developmentally regulated at a transcriptional or post-transcriptional level in the fat body.
一组结构相关的蛋白质，被称为“30K蛋白质”，以阶段依赖的方式在家蚕（Bombyx mori）幼虫的血淋巴中积累。为了研究脂肪体中30K蛋白质生物合成的调控机制，编码这些血浆蛋白的mRNA序列被克隆，并研究了它们在幼虫发育过程中的结构和表达。从五龄中期幼虫脂肪体的聚腺苷酸RNA构建的cDNA文库中分离出五个质粒克隆，每个克隆携带一个编码30K蛋白质组分的独特mRNA序列。这些克隆在核苷酸和氨基酸序列方面彼此非常相似。每个克隆都带有一个编码251至264个氨基酸残基的开放阅读框，在推导的氨基末端结构域有一个典型的跨膜分泌信号序列。Northern印迹杂交提供的证据表明，脂肪体中30K蛋白质mRNA量的发育变化很好地反映了30K蛋白质血淋巴浓度的变化，这表明30K蛋白质的生物合成在脂肪体中在转录或转录后水平受到发育调控。
