Casanova J, Furriols M, McCormick C A, Struhl G
Centre d'Investigaciö i Desenvolupament (CSIC), Barcelona, Spain.
Genes Dev. 1995 Oct 15;9(20):2539-44. doi: 10.1101/gad.9.20.2539.
The basic body plan of Drosophila is specified by four determinant systems that organize pattern along the anteroposterior and dorsoventral axes. Two of these systems (anterior and posterior) depend on localized mRNAs. In contrast, the other two (ventral and terminal) require locally generated extracellular ligands that are transduced, respectively, by the transmembrane receptors Toll and torso (tor). The ligand for the Toll receptor is thought to be spätzle (spz), a secreted protein that is activated by proteolytic cleavage. Here we report that trunk (trk), a gene required for activity of the tor receptor, encodes a protein that resembles spz in several respects. In particular, the sequence suggests that trk is a secreted protein and that it contains an internal site for proteolytic cleavage. Furthermore, the carboxy-terminal domain of trk has a similar arrangement of cysteines to that of spz. We propose that trk encodes an extracellular ligand involved in specifying terminal body pattern and suggest by analogy with spz that a cleaved form of trk constitutes the ligand for the tor receptor.
果蝇的基本身体结构由四个决定系统指定，这些系统沿着前后轴和背腹轴组织模式。其中两个系统（前部和后部）依赖于局部化的mRNA。相比之下，另外两个系统（腹侧和末端）需要局部产生的细胞外配体，它们分别由跨膜受体Toll和躯干（tor）转导。Toll受体的配体被认为是spätzle（spz），一种通过蛋白水解切割而被激活的分泌蛋白。在这里我们报告，trunk（trk）是tor受体活性所需的一个基因，它编码的一种蛋白质在几个方面类似于spz。特别是，序列表明trk是一种分泌蛋白，并且它含有一个蛋白水解切割的内部位点。此外，trk的羧基末端结构域的半胱氨酸排列与spz相似。我们提出trk编码一种参与指定末端身体模式的细胞外配体，并通过与spz类比表明trk的一种切割形式构成tor受体的配体。
