Electrostatic calculations and model-building suggest that DNA bound to CAP is sharply bent.
Two observations suggest that DNA, upon binding to E. coli catabolite gene activator protein (CAP), is sharply bent by a total angle of at least 100-150 degrees: (1) The electrostatic potential field of CAP shows regions of positive potential that form a ramp on 3 sides of the protein. (2) The DNA binding site size as determined by DNA ethylation interference with binding, (Majors: "Control of the E. coli Lac Operon at the Molecular Level." Ph.D. Thesis, Harvard University, Cambridge, 1977) and by relative affinities of DNA fragments of various lengths (Liu-Johnson et al.: Cell 47:995-1005, 1986) requires severe bending of the DNA to maintain its favorable electrostatic contact with the protein.
Warwicker
J
J
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511.
Engelman
B P
BP
Steitz
T A
TA
D001426:Bacterial Proteins / Q000378:metabolism*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002373:Cyclic AMP Receptor Protein / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D012318:RNA Polymerase I / Q000378:metabolism
D001426:Bacterial Proteins; D002373:Cyclic AMP Receptor Protein; D004269:DNA, Bacterial; D012318:RNA Polymerase I