Abstract
The formation of proteinβDNA complexes often involves deformation of the DNA double helix. We have calculated the energy necessary to produce this deformation in 71 crystallographically determined complexes, using internal coordinate energy optimization with the JUMNA program and a generalized Born continuum solvent treatment. An analysis of the data allows deformation energy to be interpreted in terms of both local and global structural changes. We find that, in the majority of complexes, roughly 60% of the deformation energy corresponds to backbone distortion. It is also found that large changes in stacking and pairing energies are often compensated for by other, longer range, stabilizing factors. Some deformations, such as base opening, can be large, but onlyβproduce local energetic effects. In terms of backbone distortions, the angle Ξ±, most often involved in Ξ±Ξ³ transitions, makes the most significant energetic contribution. This type of transition is twice as costly as those involving Ξ², or coupled Ρ΢ changes. Sugar amplitude changes are also energetically significant, in contrast to changes in phase angles. Β© 2003 Wiley Periodicals, Inc. Biopolymers 70: 414β423, 2003