FIG. 6.

Restriction of Fv1 mix-and-match mutants in the transduction assay. The mix-and match mutants are named with three letters; the first and second letters stand for the allelic origin of the amino acids at positions 358 and 399, respectively, and the last letter indicates the allelic origin of the C terminus. The extent of restriction is as follows: +, restriction; (+), slightly less restriction (example, Fv1^b on NB-tropic viruses [Fig. 3]); (−), slight inhibition (example, Fv1^b on B-tropic viruses); −, no restriction. Essentially identical results were obtained on both M. dunni and CCL-64 cells.