Sequences are aligned against HXB2 and a subtype C consensus sequence derived from the 2007 LANL database. Numbering is based on HXB2. MSD denotes start of the Membrane Spanning Domain. Consensus residues are color-coded by degree of conservation (red >98%, orange 90–97.9%, yellow 75–89.9%, green <75%). In panel A, IC50 for mAb 4E10 is expressed as a range for all functional clones tested for each MPER variant. Positions 677, 680, 683, and 686 are color-coded for emphasis. In Panel B, Env protein sequences have been color-coded according to charge at positions 677, 680, and 683 (blue = basically charged residue, yellow = uncharged residue). All other residues (in white) are uncharged.