FIG. 8.

Summary of the amino acid residues in the SR-A ALV SU hypervariable regions identified as important for Tva receptor binding affinity and specificity. The amino acids identified by genetic selection strategies in replicating ALV in avian cells (23, 24; this study) are boldfaced. The basic amino acids in hr2 identified in studies using mammalian cells expressing the ALV glycoprotein mutants as well as murine leukemia virus vectors pseudotyped with the ALV glycoproteins to measure infectivity are underlined (11, 31).