Open AccessThe structure of a CAP–DNA complex having two cAMP molecules bound to each monomer
Author(s) -
J.M. Passner,
Thomas A. Steitz
Publication year - 1997
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.94.7.2843
Subject(s) - dna , dna binding domain , helix (gastropod) , hmg box , binding site , activator (genetics) , monomer , chemistry , protein structure , catabolite repression , dna clamp , stereochemistry , biology , biophysics , dna binding protein , biochemistry , gene , transcription factor , rna , mutant , ecology , organic chemistry , snail , polymer , reverse transcriptase
The 2.2 A resolution crystal structure of the Escherichia coli catabolite gene activator protein (CAP) complexed with cAMP and a 46-bp DNA fragment reveals a second cAMP molecule bound to each protein monomer. The second cAMP is in the syn conformation and is located on the DNA binding domain interacting with the helix-turn-helix, a beta-hairpin from the regulatory domain and the DNA (via water molecules). The presence of this second cAMP site resolves the apparent discrepancy between the NMR and x-ray data on the conformation of cAMP, and explains the cAMP concentration-dependent behaviors of the protein. In addition, this site's close proximity to mutations affecting transcriptional activation and its water-mediated interactions with a DNA recognition residue (E181) and DNA raise the possibility that this site has biological relevance.