The Molecular Recognition Mechanism of Nucleic Acid Structure by Beta-Turn Motif of Protein

到目前为止，蛋白质对DNA碱基序列有四种不同的识别基序：螺旋-转角-螺旋、β-折叠、锌指和亮氨酸拉链。Suzuki M.预计在海胆生精组蛋白中有一种全新的模式。H1和H_2B。DNA结合臂由Ser-Pro-Lys(Arg)-Lys(Arg)残基的重复序列组成。从氨基酸序列来看，该区域可能采用β-转角结构，从而提供了新的识别机制。X-射线结构分析确定了该复合体的原子级分子结构：(1)化学合成了含有该串联氨基酸序列的4个寡肽片段，它们对应于狭角对虾H1的N-末端区域。化学合成了几种分子中心带有腺嘌呤(-酪胺)轨迹的寡核苷酸。用这些化合物对配合物进行了几次结晶，但到目前为止还没有得到适合于X射线分析的晶体。基于核磁共振谱和计算机图形学系统，确定了抗生素色霉素与DNA齐聚物的络合物结构。该模型提供了药物对DNA碱基序列的识别机制，这是一种非常新颖的基序，是一种广泛存在的疏水表面相互作用。(3)开发了DNA-蛋白质复合体结构参数计算和绘制的计算机程序，该程序适用于表征复合体相互作用。

To date there are four different recognition motifs of DNA base sequence by protein, helix-turn-helix, beta-sheet, Zn-finger and leucin zipper. By Suzuki M., a quite new mode is expected in sea urchin spermatogenic histones. H1 and H2B. The DNA-binding arms are composed of repeats of Ser-Pro-Lys (Arg)-Lys (Arg) residues. From amino acid sequence, this region may adopt the beta-turn structure, so this offers the novel recognition mechanism. X-ray structure analysis determines the molecular structure at atomic level of this complex formation.(1) Four oligopeptide fragments containing this tandem amino acid sequence were chemically synthe-sized, which correspond to the N-terminal region of H1 of P. angulosus. Several oligonucleotides which have adenine (-tymine) track at the central region in molecule were also chemically synthesized. Several crystallizations of complex by using these compounds have been done, but to date no suitable crystal for X-ray analysis has been obtained. A series of investigations about complex formation in solution are necessary.(2) The complex structure of antibiotic Chromomycin and DNA oligomer was determined based on NMR spectra and computer graphics system. This model offers the recognition mechanism of DNA base sequence by drug which is quite novel motif, a widely spread hydrophobic surface interaction.(3) A computer program of calculating and drawing the structural parameters for DNA-protein complex was developed and is suitable to characterize the complex interaction.