Identification of the regions of Fv1 necessary for murine leukemia virus restriction

The Fv1 gene restricts murine leukemia virus replication via an interaction with the viral capsid protein. To study this interaction, a number of muta tions, including a series of N-terminal and C-terminal deletions, internal deletions, and a number of single-amino-acid substitutions, were introduced into the n and b alleles of the Fv1 gene and the effects of these changes on virus restriction were measured. A significant fraction of the Fv1 prote in was not required for restriction; however, retention of an intact major homology region as well as of domains toward the N and C termini was essent ial. Binding specificity appeared to be a combinatorial property of a numbe r of residues within the C-terminal portion of Fv1.