Comparison of the wild type and ΔQ44 Vpr mutant structures. Stereoview of the three dimensional structure of the wild type Vpr determined by NMR (A) and theoretical model for the Vpr ΔQ44 mutant (B). Helices (17–33), (38–50) and (54–77) are represented as ribbon and colored in blue, pink and green, respectively and loops (34–37) and (51–53) are colored in yellow. For clarity, the two disordered extremities of the molecule have not been represented. Residues showing long range correlations on NOESY NMR experiments have been displayed in the stick representation and colored according to their hydrophobicity. Only their side chain atoms have been represented. The network of hydrophobic residues can be observed at the interface of the three α-helices. Note the impact of the ΔQ44 deletion (B) on the partial unfolding of the second helix and the rearrangement of the hydrophobic residues at the interface.