Open AccessCrystal structure of intercalated four-stranded d(C3T) at 1.4 A resolution.
Author(s) -
ChulHee Kang,
Imre Berger,
Curtis Lockshin,
Robert L. Ratliff,
Robert K. Moyzis,
Alexander Rich
Publication year - 1994
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.91.24.11636
Subject(s) - cytosine , crystallography , molecule , chemistry , protonation , stereochemistry , crystal (programming language) , crystal structure , twist , covalent bond , duplex (building) , dna , phosphate , ion , geometry , biochemistry , mathematics , organic chemistry , computer science , programming language
The crystal structure of d(C3T), solved at 1.4 A resolution, reveals that the molecule forms a four-stranded intercalated complex. It consists of two parallel-stranded duplexes, each of which is held together by cytosine-protonated cytosine base pairs. The two duplexes are intercalated with each other and have opposite strand orientation. The molecule has a flat, lath-like appearance, and the covalently bonded cytosines have a slow right-handed twist of 17.1 degrees. However, there is considerable asymmetry. On one of the flat sides, the phosphate groups are rotated away from the center of the molecule. They are held in this orientation by bridging water molecules that bind the NH of cytosine and a phosphate group of an opposite chain. There is also considerable microheterogeneity in the structure. The cytosine hemiprotonation occurs even at pH 7 where stable crystals form.