Computational anti-AIDS drug design based on the analysis of the specific interactions between immunophilins and the HIV-1 gp120 V3 loop. Application to the FK506-binding protein.

The object of the study was to model the structural complex of the FK506-binding protein (FKBP) with the CRK peptide imitating the central region of the HIV-1 V3 loop, as well as to define the FKBP stretch giving rise to the binding site for V3 the synthetic copy of which, on the assumption of preserving the spatial peptide structure in the free state, can be considered as a promising applicant for the role of antiviral drug. To this end, the following successive steps were carried out: (i) the NMR-based conformational analysis of CRK was put into practice, and, in the light of the results derived, the best energy CRK structure meeting the requirements of the input NMR data was identified; (ii) molecular docking of the CRK structure with the X-ray FKBP conformation was implemented, and energy refining the simulated structural complex was realized; (iii) the matrix of distances between amino acids of the ligand and receptor was computed to specify the FKBP stretch keeping in touch with CRK followed by analyzing the types of interactions stabilizing the over-molecular ensemble; (iv) 3D structure of this stretch in the unbound status referred to as the FKBP peptide was predicted, and its collation with the X-ray conformation of the identical FKBP site was performed; (v) the potential energy function and its constituents were studied for the structural complex generated by molecular docking of the CRK molecule with the FKBP peptide; and (vi) from all evidence, the virtual FKBP-derived peptide was submitted to be utilized as a prospective structural framework in the anti-HIV-1 drug design. Summing up the results obtained, the following principal conclusion was drawn: a high affinity of the V3 loop peptide to the FKBP is based on the principle of "mirror similarity" that implies the near resemblance of 3D structures for the two individual fragments of the receptor and ligand, which, most likely, accounts for recognizing the immunophilin by V3 and determines the specificity of their efficacious interactions arising from the experimental observations.