NMR-STUDY OF THE PEPTIDE PRESENT IN THE PRINCIPAL NEUTRALIZING DETERMINANT (PND) OF HIV-1 ENVELOPE GLYCOPROTEIN GP120

The peptide sequence Gly-Pro-Gly-Arg-Ala-Phe (GPGRAF) is present in ma ny principal neutralizing determinants (PND) of the human immunodefici ency virus type-1 (HIV-1). It has been shown that peptides from the PN D sequence contain a significant beta turn in the conserved Gly-Pro-Gl y-Arg sequence. In order to find out whether or not the smaller subuni ts also contain this turn, we have studied the NMR of a hexapeptide [G PGPRAF, peptide (I)], a heptapeptide Gly-Pro-Gly-Arg-Ala-Phe-Cys [GPGR AFC, peptide (II)] and a dodecapeptide [GPGRAFGPGRAF, peptide (III)], retaining the side chain protecting groups. Although the majority of c onformations for these peptides are disordered, there is a considerabl e propensity of structures with beta turn in the GPGR sequence. While peptide (I) and peptide (III) seem to have both type I and type II bet a turn conformations, peptide (II) shows a propensity of only type II beta turn. The nascent structures obtained in these peptides may get s tabilized as the receptor binding conformation in the presence of the receptors, thus playing a significant role in vaccine development agai nst HN. (C) 1997 Elsevier Science B.V.