Timsit Y, Vilbois E, Moras D
Laboratoire de Cristallographie Biologique, Institut de Biologie Moléculaire et Cellulaire, Strasbourg, France.
Nature. 1991 Nov 14;354(6349):167-70. doi: 10.1038/354167a0.
the crystal packing of the B-DNA dodecamer d(ACCG-GCGCCACA).d(TGTGGCGCCGGT) is characterized by the reciprocal fit of double helices with specific base-backbone interactions in the major groove. Cooling the crystals below -10 degrees C stabilizes a new conformational state with a long-range sequence-dependent one-step shift in the major-groove base pairing. The tilt of the bases leads to the disruption of the Watson-Crick pairing in the major groove and to the formation of interactions with the 5' neighbour of their complement. This alteration propagates along the helical axis over more than half a turn. As a result, the molecular structure is normal when seen from the minor groove side and mismatched in the major groove. Comparison with a parent isomorphous dodecamer structure corresponding to the codon 10-13 of the c-Ha-ras proto-oncogene show that this new structural feature is sequence dependent and clearly favoured by (CA)n tracts. As(CA)n tracts of DNA are involved both in recombination and in transcription, this new recognition pattern should be considered in the analysis of the various processes involving the reading of the genetic information.
B-DNA十二聚体d(ACCG-GCGCCACA).d(TGTGGCGCCGGT)的晶体堆积特征在于双螺旋的相互契合以及在大沟中特定的碱基-骨架相互作用。将晶体冷却至-10摄氏度以下会稳定一种新的构象状态，其大沟碱基配对中存在长程序列依赖性的一步位移。碱基的倾斜导致大沟中沃森-克里克配对的破坏，并与它们互补链的5'邻位形成相互作用。这种改变沿螺旋轴传播超过半圈。结果，从小沟侧看分子结构正常，而在大沟中不匹配。与对应于c-Ha-ras原癌基因密码子10-13的亲本同晶型十二聚体结构相比表明，这种新的结构特征是序列依赖性的，并且明显受到(CA)n序列的青睐。由于DNA的(CA)n序列参与重组和转录，在分析涉及遗传信息读取的各种过程时应考虑这种新的识别模式。
