Hart A C, Krämer H, Zipursky S L
Howard Hughes Medical Institute, Department of Biological Chemistry, University of California, Los Angeles 90024.
Nature. 1993 Feb 25;361(6414):732-6. doi: 10.1038/361732a0.
The fate of the R7 photoreceptor cell in the Drosophila compound eye is established by a specific inductive interaction between the R8 photoreceptor neuron and the R7 precursor cell. This induction is mediated by two cell-surface proteins: the ligand, bride of sevenless (boss), and sevenless (sev), a tyrosine-kinase receptor. The structure of boss is unique for a ligand of a tyrosine-kinase receptor. It contains a large extracellular domain, seven transmembrane segments, and a carboxy-terminal cytoplasmic tail. Here we report that: (1) boss activates tyrosine phosphorylation of the sev receptor; (2) the seven transmembrane domain of boss is necessary for its function; and (3) a soluble form of boss acts as an antagonist of the sev receptor both in vivo and in vitro.
果蝇复眼中R7光感受器细胞的命运是由R8光感受器神经元与R7前体细胞之间特定的诱导性相互作用所决定的。这种诱导作用由两种细胞表面蛋白介导：配体“无七之新娘”（boss）和酪氨酸激酶受体“无七”（sev）。boss的结构对于酪氨酸激酶受体的配体而言是独特的。它包含一个大的细胞外结构域、七个跨膜区段以及一个羧基末端胞质尾。在此我们报告：（1）boss激活sev受体的酪氨酸磷酸化；（2）boss的七个跨膜结构域对其功能是必需的；（3）可溶性形式的boss在体内和体外均作为sev受体的拮抗剂发挥作用。
