Conservation of the amino acids within the motif. (A) The y-axis is in bits, which is equal to the relative entropy of the motif in relation to a uniform background frequency model. (B) The figure is a schematic representation of regions within the ectodomain of gp41. Starting from the N terminus is the FP, N-heptad repeat (NHR), loop, CHR, and TMD. The location of the motif is presented, as well as the peptides derived from that region (peptides 1-4). Residue numbers and sequence correspond to the HXB2 HIV-1 gp160 variant.