Tyr26 and Phe73 are essential for full biological activity of the Fd Gene 5 protein

M. J. O'Donohue, G. P. Scarlett, G. G. Kneale*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Pages (from-to)219-223
Number of pages5
JournalFEMS Microbiology Letters
Issue number2-3
Publication statusPublished - 1 May 1993


  • Base stacking
  • DNA binding protein
  • Filamentous bacteriophage
  • Gene 5 protein
  • Saturation mutagenesis
  • Single-stranded DNA

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