Protein and DNA-sequence homologies between the V3-loop of human immunodeficiency virus type I envelope protein gp120 and immunoglobulin variable regions.

We found that a common amino acid sequence motif exists between the V3-loop region of the human immunodeficiency virus type I envelope protein HIV gp120 and the human immunoglobulin heavy chain variable regions of subclass III (Ig VH-III). In the Ig VH-III sequences, the common motif overlaps with framework-1, complementarity-determining-region-1 and framework-2. In the homologous regions, the two groups of sequences also have a similar distribution of residue variability. On the DNA sequence level, the homology includes the conserved rearrangement signals of the VH-III genes, which lends support to the speculation that the V3 region of gp120 also may be involved in rearrangement processes.