THEORETICAL-STUDY OF 3-DIMENSIONAL STRUCTURE OF THE ALA-SER-THR-THR-THR-ASN-TYR-THR SEGMENT IN HIV-PROTEIN-GP120 RESPONSIBLE FOR VIRUS BINDING TO THE T4-RECEPTOR

The method of ''restricted'' molecular dynamics combining the algorith ms of theoretical conformational analysis and the NMR data was used to model the 3D structure of fragment 4-11 of a vasoactive intestinal pe ptide analog [VIP'(4-11)] homologous to peptide T, an HIV reproduction inhibitor corresponding to the T4-receptor-binding site in the viral coat protein gp120. VIP'(4-11) in methanal-water (1:1) was shown to ac quire a conformation of a-helix distorted over Ala4-Asp8 and nearly id eal in Asn9-Thr11. The resulting model was collated with the 3D struct ure of peptide T computed earlier and the crystalline conformations of homologous regions 19-26 in RNase A and 169-176 in penicillopepsin, t o infer the most probable structure of the gp120 stretch Thr-Thr-Asn-T yr-Thr (C-terminal segment of peptide T). On the strength of the data obtained, it was concluded that the gp120 segment Ala-Ser-Thr-Thr-Thr- Asn-Tyr-Thr responsible for virus binding to the T-cell surface assume s one of the conformations characteristic of isolated peptide T.