Conformational analysis by NMR and molecular modelling of the 41-62 hydrophilic region of HIV-1 encoded virus protein U (Vpu). Effect of the phosphorylation on sites 52 and 56

The peptide of 22 amino acid residues, Vpu_P41-62, phosphorylated at the tw o sites Ser(52) and Ser(56) has been implicated in the degradation of CD4 r eceptor molecules, an important stage of the pathways to human immunodefici ency virus type: 1 pathology (HIV-1). In order to assess the structural inf luence of phosphorylation, a conformational analysis by NMR and molecular s imulation have been carried out for the phosphorylated Vpu_P41-62, and non- phosphorylated Vpu(41-62) in both H2O (at pH 3.5 and 7.2) and a 1:1 mixture of H2O and trifluoroethanol. Analysis of the short-, medium-range NOE conn ectivities and of the secondary chemical shifts indicated that the peptide segment (42-49) shows a less well-defined helix propensity. The 50-62 segme nt forms a loop with the phosphate group pointing away, a short P-strand an d a flexible extended 'tail' of residues 60-62. Differences in this molecul ar region 50-62 suggest that conformational changes of Vpu_P, play a potent ial role in Vpu_P-induced degradation of CD4 molecules. (C) 2001 Academic d es sciences/Editions scientifiques et medicales Elsevier SAS.