Tyr26 and Phe73 are essential for full biological activity of the Fd Gene 5 protein
Résumé
Using site-saturation mutagenesis, we have established all possible amino acid substitutions at Tyr26 and Phe73 that are
compatible with biological activity of the gene 5 protein in vivo. No substitutions were found at either site that gave rise to a fully
functional gene 5 protein, indicating that these two amino acid residues are crucial. However, partial activity was found if either
residue was replaced by another aromatic amino acid (Y26F, Y26W, F73Y, F73W). The results suggest that both Tyr26 and Phe73
are important for base stacking in the nucleoprotein complex. The functional consequences of the removal of the hydroxyl group
from Tyr26 argue that this residue may, in addition, be involved in hydrogen bond formation to confer greater stability on the
complex. In contrast, the addition of such a group to Phe73 reduces activity.