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Flexibility of Terminal Cytidines in Ca 2+ Form B‐DNA
Author(s) -
Luo Zhipu,
Dauter Zbigniew
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.710.15
Subject(s) - dodecameric protein , dna , cytidine , duplex (building) , base pair , crystallography , long terminal repeat , chemistry , stereochemistry , biology , microbiology and biotechnology , biochemistry , genome , gene , enzyme
The first B‐DNA duplex crystal structure of dodecamer d(CGCGAATTCGCG) 2 was solved in early 1980s by Richard Dickerson 1 . Subsequently, hundreds of B‐DNA structures were revealed by X‐ray crystallography according to the Protein Data Bank 2 , and most of those structures were crystallized with Mg 2+ . Only few B‐DNA crystal structures involved the binding of Ca 2+ , which resulted in unpairing of the terminal base‐pair at each end by coordinating the terminal guanines and bend backward inserting into the minor groove of adjacent duplexes 3,4 . However, the terminal cytidine at each end of duplex were not observed in previous Ca 2+ form B‐DNA, even at 1.3 Å high resolution data 4 . Here, we report two crystal structures of d(CGCGAATTCGCG) 2 in presence of Ca 2+ at resolutions of 1.8 Å and 1.55 Å. The lower resolution structure shows one terminal cytidine at one end, and the higher resolution structure presents both terminal cytidines at each end of duplex. The orientations of terminal cytidines are completely different, which demonstrates the flexibility of terminal cytidines in Ca 2+ form of the Dickerson‐Drew B‐DNA oligomer.