Raison d'être and structural model for the B‐Z transition of poly d(G‐C)∗poly d(G‐C)

FEBS Letters

Heinemann, Udo¹  Saenger, Wolfram¹ 

[1] Institüt für Kristallographie, Freie Universität Berlin, Takustraße 6, D-1000 Berlin 33, Germany

关键词: DNA;    A-;    DNA;    B-;    DNA;    Z-;    B-Z transition;    Poly d(G-C)·poly d(G-C);   

DOI  :  10.1016/0014-5793(89)81539-X

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

In DNA oligonucleotides crystallized in the A form, the nucleotides adopt standard conformation except for steps 5'-CpG-3' where reduced base-pair twist and a sliding motion of the base pairs along their long axes causes pronounced interstrand guanine-guanine overlap. As a consequence, torsion angles α,β and γ are consistently trans, trans, trans instead of the common -gauche, trans, + gauche. This conformation significantly increases the intraresidue distance between the guanine base and the 5'-phosphate group. A molecular model of poly d(G-C)·poly d(G-C) built with these structural characteristics in the A form, which we call A²-DNA, shows that rotation of the guanosine sugar into the syn orientation is easily achieved and pushes the base pair across the helix axis. If successive guanosines are changed this way, a smooth transformation occurs to the left-handed Z-DNA. We suggest that A- and A²-DNA forms of poly d(G-C)·poly d(G-C) are metastable and that the actual transition is B ⇌ (A ⇌ A²) ⇌ Z-DNA.

【 授权许可】

Unknown