Li S F, Parish R W
School of Botany, La Trobe University, Melbourne, Victoria, Australia.
Plant J. 1995 Dec;8(6):963-72. doi: 10.1046/j.1365-313x.1995.8060963.x.
Two novel myb-like genes (atmyb6 and atmyb7) were isolated from an Arabidopsis thaliana cDNA library. The entire proteins or the Myb domains encoded by the genes were expressed as fusion proteins in Escherichia coli. The DNA-binding domain of the murine c-Myb was also expressed in the same way for use in comparative studies. The fusion proteins were examined for their DNA-binding activity using the animal c-Myb DNA-binding site (MBS) and the binding site of the maize P gene product (PBS). The Myb domain of Atmyb6 bound to PBS more efficiently than to MBS. Complete Atmyb6 and Atmyb7 proteins preferentially bound to PBS but not MBS. This suggests that the in vitro binding consensus sequences for both Atmyb6 and Atmyb7 are similar to PBS. The binding of the Myb domain of Atmyb6 to both PBS and MBS raises the possibility that the protein recognizes multiple sequences in vivo. The third alpha-helix and three adjacent amino acids in the third repeat (R3) of c-Myb was replaced with the analogous sequence of Atmyb6 to create a chimeric Myb protein. This chimeric protein bound to PBS with a low affinity but failed to bind to MBS. Thus the binding pattern of the chimeric Myb protein is similar to that of the Atmyb6. This result suggests that the last 20 amino acids in the R3 repeat of Atmyb6 play a major role in DNA-binding.
从拟南芥cDNA文库中分离出两个新的类myb基因（atmyb6和atmyb7）。这些基因编码的完整蛋白质或Myb结构域在大肠杆菌中作为融合蛋白表达。鼠源c-Myb的DNA结合结构域也以同样的方式表达用于比较研究。使用动物c-Myb DNA结合位点（MBS）和玉米P基因产物的结合位点（PBS）检测融合蛋白的DNA结合活性。Atmyb6的Myb结构域与PBS的结合效率高于与MBS的结合效率。完整的Atmyb6和Atmyb7蛋白优先结合PBS而非MBS。这表明Atmyb6和Atmyb7在体外的结合共有序列与PBS相似。Atmyb6的Myb结构域与PBS和MBS的结合增加了该蛋白在体内识别多个序列的可能性。将c-Myb第三个重复序列（R3）中的第三个α-螺旋和三个相邻氨基酸替换为Atmyb6的类似序列，构建了一个嵌合Myb蛋白。该嵌合蛋白与PBS的结合亲和力较低，但不能与MBS结合。因此，嵌合Myb蛋白的结合模式与Atmyb6相似。这一结果表明，Atmyb6的R3重复序列中的最后20个氨基酸在DNA结合中起主要作用。
