CAP binding to B and Z forms of DNA

Michael G. Fried, Hen ming Wu, Donald M. Crothers

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17 Scopus citations


We have examined the interaction between the cyclic AMP receptor protein (CAP) and a small DNA fragment containing its specific recognition sequence by circular dichroism spectroscopy. The binding of CAP to this fragment induces a B to "C-like" change in the CD spectrum, which is different from that observed for non-specific binding. A one-to-one (CAP dimer to DNA) binding stoichiometry was deduced from spectroscopic titration data, as was a non-specific binding site size of 17 bp/dimer. In addition, we have compared the non-specific binding affinity of CAP for the B and Z forms of synthetic DNA copolymers. A slight preference for the B form was found. These results do not support the recent specific suggestion that CAP binds to a left-handed form of DNA (1), but indicate more generally that an optically detectable conformational change takes place in DNA on binding CAP.

Original languageEnglish
Pages (from-to)2479-2494
Number of pages16
JournalNucleic Acids Research
Issue number8
StatePublished - Apr 25 1983

Bibliographical note

Funding Information:
ACKNOWLEDGEMENTS This work was Science Foundation, of Health.

ASJC Scopus subject areas

  • Genetics


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