FIG. 1.

Sequence conservation near the proline-rich domain of MuLV SUs. Residues matching that of the Fr-MuLV sequence are indicated with a hyphen; Pro residues are underlined; gaps introduced for alignment have been left blank. The first group of sequences are from ecotropic envs; the second group are from envs of other receptor classes. F-MLV (16); M-MLV (45); A-MLV (18); HO-MLV (49); RAD-MLV (22); CAS-MLV (42); FrNx-MCF (1); M-MCF (5); r35-MCF (41); 1233-MCF (46); NZB-XENO (27); 4070-AMP and 10A1 (30).