Characterisation of HIV-1 variants.
A) Partially processed Gag-derived products detected by SDS-PAGE. Iodixanol gradient purified particle preparations of the indicated HIV-1 variants were separated on 12.5% SDS gels. Virion-associated proteins were visualized by silver staining according to standard procedures, showing MA and CA containing Gag derivatives as the most prominent bands. Lanes in the left panel were combined from two independent gels and were size adjusted for comparison. The right panel illustrates incomplete processing at the CA-SP1 boundary for variant MA-CA. Positions of molecular mass standards (in kDa) are indicated to the left. B) Central sections of 0.8 nm thickness from 6 µm defocus tomographic reconstructions of the HIV-1 variants analyzed. White arrowheads point to the immature CA layer, whereas white arrows point to the NC-RNA layer. Immature, MA-p6 and CA-p6 variants show both CA and NC-RNA layers. In CA-p6 the distance between the CA layer and the membrane is more variable. In MA-SP1 and MA-CA, the CA layer is seen, but the NC-RNA has condensed. CA-SP1 and the mature virus do not show the characteristic striated CA layer. The scale bar is 50 nm.