SOLUTION STRUCTURE OF PEPTIDES FROM HIV-I VPR PROTEIN THAT CAUSE MEMBRANE PERMEABILIZATION AND GROWTH ARREST

Vpr, one of the accessory gene products encoded by HIV-1, is a 96-resi due protein with a number of functions, including targeting of the vir al pre-integration complex to the nucleus and inducing growth arrest o f dividing cells. We have characterized by 2D NMR the solution conform ations of bioactive synthetic peptide fragments of Vpr encompassing a pair of H(F/S)RIG sequence motifs (residues 71-75 and 78-82 of HIV-1 V pr) that cause cell membrane permeabilization and death in yeast and m ammalian cells. Due to limited solubility of the peptides in water, th eir structures were studied in aqueous trifluoroethanol. Peptide Vpr(5 9-86) (residues 59-86 of Vpr) formed an alpha-helix encompassing resid ues 60-77, with a kink in the vicinity of residue 62. The first of the repeated sequence motifs (HFRIG) participated in the well-defined alp ha-helical domain whereas the second (HSRIG) lay outside the helical d omain and formed a reverse turn followed by a less ordered region. On the other hand, peptides Vpr(71-82) and Vpr(71-96), in which the seque nce motifs were located at the N-terminus, were largely unstructured u nder similar conditions, as judged by their (CH)-H-alpha chemical shif ts. Thus, the HFRIG and HSRIG motifs adopt alpha-helical and turn stru ctures, respectively, when preceded by a helical structure, but are la rgely unstructured in isolation. The implications of these findings fo r interpretation of the structure-function relationships of synthetic peptides containing these motifs are discussed. (C) 1998 European Pept ide Society and John Wiley & Sons, Ltd.