Dipole-dipole interactions in protein-protein complexes: a quantum mechanical study of the ubiquitin-Dsk2 complex

Quantum mechanical calculations are performed on the proteins that constitute the ubiquitin-Dsk2 complex whose atomic structure has been experimentally determined by NMR spectroscopy (PDB id 1WR1). The results indicate that the dipole moment vectors of the two proteins are aligned in a head-to-tail orientation while forming and angle of ~130{\deg}. Hence, attractive dipole-dipole interactions not only stabilize the protein-protein complex but they are likely to favor the correct orientation of the proteins during the formation of the complex.