The Vpr protein of human immunodeficiency virus type 1 binds to nucleocapsid protein p7 in vitro

The Vpr protein of human immunodeficiency virus type 1 (HIV-1) is incorporated into the virion by the Gag polyprotein precursor Pr55gag. The importance of the p6gag sequence at the C-terminal end of Pr55gag has a crucial role in Vpr incorporation. To identify the Gag sequences directly involved in Vpr binding, we compared the Vpr binding affinities of the 71 amino acid nucleocapsid protein p7, the C-terminal peptide (35-71) p7C and p6gag by affinity chromatography. p7 and p7C have the strongest Vpr binding activities compared to p6gag. These results suggest that the nucleocapsid protein and its C-terminal domain may be important for the incorporation of Vpr into the mature HIV-1 virion and the subsequent localisation of viral nucleic acid to the cell nucleus by Vpr.