FIG. 4.

Chimeric virus V3 sequences and alignment of A2 and D2 gp120 proteins. (A) V3 regions of a number of chimeric virus gp120 ORFs were sequenced from the pHXB2 constructs, shown in the single-letter amino acid code. The consensus sequence was derived from the V3 sequences of the pCDNA3-gp120 ORFs (data not shown), and numbering is based on MN gp120. Residues 11 and 25, previously implicated in determining the non-syncytium-inducing (NSI)/R5 syncytium-inducing (SI)/X4 phenotype, are underlined, and any residues which vary from the consensus are highlighted in bold. Residues which do not vary from the consensus are shown as dashes. (B) Peptide translation (single-letter amino acid code) of two pairs of gp120 sequences with different coreceptor usage, two clones obtained from the A2 sample and two from D2. For the second sequence in each pair, only the different positions are shown. The upper sequence in each pair is R5 tropic, and the lower is X4 tropic.