“…Davey, Zuo, and Cunningham recently proposed that serine 84, aspartate 86, and tryptophan 102 in Friend MLV (corresponding to serine 82, aspartate 84, and tryptophan 100 in Mo MLV) form the core of the binding site for both tyrosine 235 and glutamic acid 237 on the receptor (5). They based this proposal on three points: first, that binding and infection were reduced by certain changes in these residues (5,13); second, that the three residues were adjacent on the surface of folded SU (7); and third, that the only critical receptor residues were tyrosine 235 and glutamic acid 237, from which erroneous assumption they concluded that any receptor binding site found on SU must be the site for these residues. However, Albritton and coworkers and Yoshimoto and coworkers had previously shown that at least two more receptor residues, asparagine 232 and valine 233, are involved in infection (1,18).…”