Rousseau Philippe, Loot Céline, Guynet Catherine, Ah-Seng Yoan, Ton-Hoang Bao, Chandler Mick
Laboratoire de Microbiologie et Génétique Moléculaire (UMR 5100 CNRS - U.Toulouse-3), 118 rte. de Narbonne, Bât. IBCG, 31062 Toulouse Cedex 09, France.
Mol Microbiol. 2007 Mar;63(6):1701-9. doi: 10.1111/j.1365-2958.2007.05615.x.
IS911 transposition involves a closed circular insertion sequence intermediate (IS-circle) and two IS-encoded proteins: the transposase OrfAB and OrfA which regulates IS911 insertion. OrfAB alone promotes insertion preferentially next to DNA sequences resembling IS911 ends while the addition of OrfA strongly stimulates insertion principally into DNA targets devoid of the IS911 end sequences. OrfAB shares its N-terminal region with OrfA. This includes a helix-turn-helix (HTH) motif and the first three of four heptads of a leucine zipper (LZ). OrfAB binds specifically to IS911 ends via its HTH whereas OrfA does not. We show here: that OrfA binds DNA non-specifically and that this requires the HTH; that OrfA LZ is required for its multimerization; and that both motifs are essential for OrfA activity. We propose that these OrfA properties are required to assemble a nucleoprotein complex committed to random IS911 insertion. This control of IS911 insertion activity by OrfA in this way would assure its dispersion.
IS911转座涉及一个封闭的环状插入序列中间体（IS环）和两种由IS编码的蛋白质：转座酶OrfAB和调节IS911插入的OrfA。单独的OrfAB优先促进在类似于IS911末端的DNA序列旁插入，而添加OrfA则强烈刺激主要插入缺乏IS911末端序列的DNA靶标中。OrfAB与OrfA共享其N端区域。这包括一个螺旋-转角-螺旋（HTH）基序和亮氨酸拉链（LZ）四个七肽中的前三个。OrfAB通过其HTH基序特异性结合IS911末端，而OrfA则不结合。我们在此表明：OrfA非特异性结合DNA，这需要HTH基序；OrfA的LZ基序是其多聚化所必需的；并且这两个基序对于OrfA的活性都是必不可少的。我们提出，这些OrfA特性是组装致力于随机IS911插入的核蛋白复合物所必需的。以这种方式由OrfA对IS911插入活性进行的这种控制将确保其扩散。
