Figure 3.

Amino acid sequence comparison of the Env SU domains of AKR6 X-MLV, 1E P-MLV, and prototypic X-MLV and P-MLV. Amino acid alignment of the Env SU domains of NZB X-MLV [GenBank:K02730], AKR6 X-MLV [GenBank:DQ199948], 1E P-MLV [GenBank:DQ199949], and FrMCF P-MLV [GenBank:X01679]. Sequences are shown starting with the initiator methionine and include endoplasmic reticulum signal sequences of unknown lengths. Variable regions A and B, believed to be responsible for receptor recognition [45], are indicated by brackets. Non-conservative amino acids differences are indicated by black boxes and conservative changes are indicated by grey boxes. Blue boxes indicate amino acids that are identical among the P-MLVs but dissimilar from one or more of those of the X-MLVs, identical among the X-MLVs but dissimilar from one or more of those of the P-MLVs, or both. Cyan boxes indicate amino acids that are identical among the P-MLVs and similar to those of the X-MLVs, identical among the X-MLVs and similar to those of the P-MLVs, or both.