Similarities between peptides in the V3 loop of HIV-1 and conserved Plasmodium erythrocyte binding proteins. Panel A: Homologous sequences in the cysteine-rich regions of the P. falciparum erythrocyte binding protein EBA-175 (F1), P. knowlesi DBP (a), P. vivax DBP, and the V3 loop of HIV-1 strain MN. Identical or similar amino acids are boxed in yellow or green in both panels. KRKR (in green box) is a consensus glycosaminoglycan (GAG) binding sequence (BBXB, where B is a basic amino acid, K or R) in the HIV-1, P. vivax and P. knowlesi sequences. P. falciparum EBA-175 has two GAG binding sites of the BBBxxB type in tandem (underlined). Panel B: Secondary structure of the V3 loop of HIV-1 SU strain MN as determined by Sharon et al.  is shown (PDB: 1NJ0). Addition residues not contained in this structure were modeled in SWISS-MODEL (dashed oval). Structures are shown for the V3 loop-like regions of P. knowlesi DBP as determined by Singh et al.  (2C6J) and P. falciparum EBA-175 as determined by Tolia et al.  (1ZRL).