Passner J M, Ryoo H D, Shen L, Mann R S, Aggarwal A K
Structural Biology Program, Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York, New York 10029, USA.
Nature. 1999 Feb 25;397(6721):714-9. doi: 10.1038/17833.
During the development of multicellular organisms, gene expression must be tightly regulated, both spatially and temporally. One set of transcription factors that are important in animal development is encoded by the homeotic (Hox) genes, which govern the choice between alternative developmental pathways along the anterior-posterior axis. Hox proteins, such as Drosophila Ultrabithorax, have low DNA-binding specificity by themselves but gain affinity and specificity when they bind together with the homeoprotein Extradenticle (or Pbxl in mammals). To understand the structural basis of Hox-Extradenticle pairing, we determine here the crystal structure of an Ultrabithorax-Extradenticle-DNA complex at 2.4 A resolution, using the minimal polypeptides that form a cooperative heterodimer. The Ultrabithorax and Extradenticle homeodomains bind opposite faces of the DNA, with their DNA-recognition helices almost touching each other. However, most of the cooperative interactions arise from the YPWM amino-acid motif of Ultrabithorax-located amino-terminally to its homeodomain-which forms a reverse turn and inserts into a hydrophobic pocket on the Extradenticle homeodomain surface. Together, these protein-DNA and protein-protein interactions define the general principles by which homeotic proteins interact with Extradenticle (or Pbx1) to affect development along the anterior-posterior axis of animals.
在多细胞生物的发育过程中,基因表达必须在空间和时间上受到严格调控。在动物发育中起重要作用的一组转录因子由同源异型(Hox)基因编码,这些基因决定了沿前后轴的不同发育途径之间的选择。Hox蛋白,如果蝇的超双胸蛋白,自身的DNA结合特异性较低,但当它们与同源异型蛋白Extradenticle(或哺乳动物中的Pbxl)结合时,会获得亲和力和特异性。为了理解Hox-Extradenticle配对的结构基础,我们在此使用形成协同异二聚体的最小多肽,以2.4埃的分辨率确定了超双胸蛋白-Extradenticle-DNA复合物的晶体结构。超双胸蛋白和Extradenticle同源结构域结合在DNA的相对面上,它们的DNA识别螺旋几乎相互接触。然而,大多数协同相互作用来自超双胸蛋白位于其同源结构域氨基末端的YPWM氨基酸基序,该基序形成一个反向转角并插入到Extradenticle同源结构域表面的一个疏水口袋中。这些蛋白质-DNA和蛋白质-蛋白质相互作用共同定义了同源异型蛋白与Extradenticle(或Pbx1)相互作用以影响动物前后轴发育的一般原则。