FIG. 1.

Structures of chimeric FeLV-B/A-MLV envelopes and chimeric Pit1/Pit2 proteins. (A) The chimeric FeLV-B/A-MLV envelopes were generated in our previous study (35). The variable regions VRA and VRB, the proline-rich region (PRR), and the restriction sites used to generate the chimeric envelope cDNAs are indicated. The two potential disulfide-bonded loops in VRA and one disulfide-bonded loop in VRB are indicated by the loop structures. BBB and AAA represent wild-type FeLV-B and A-MLV envelopes, respectively. (B) Topological model of wild-type and chimeric Pit1 and Pit2 receptors showing the five presumptive ECLs and the large cytoplasmic loop. The chimeric Pit1/Pit2 cDNAs were generated by Miller and Miller (25).