THE HIGHLY CONSERVED AMINO-ACID-SEQUENCE MOTIF TYR-GLY-ASP-THR-ASP-SER IN ALPHA-LIKE DNA-POLYMERASES IS REQUIRED BY PHAGE-PHI-29 DNA-POLYMERASE FOR PROTEIN-PRIMED INITIATION AND POLYMERIZATION

The α-like DNA polymerases from bacteriophage ∅29 and other viruses, prokaryotes and eukaryotes contain an amino acid consensus sequence that has been proposed to form part of the dNTP binding site. We have used site-directed mutants to study five of the six highly conserved consecutive amino acids corresponding to the most conserved C-terminal segment (Tyr-Gly-Asp-Thr-Asp-Ser). Our results indicate that in ∅29 DNA polymerase this consensus sequence, although irrelevant for the 3' → 5' exonuclease activity, is essential for initiation and elongation. Based on these results and on its homology with known or putative metal-binding amino acid sequences, we propose that in ∅29 DNA polymerase the Tyr-Gly-Asp-Thr-Asp-Ser consensus motif is part of the dNTP binding site, involved in the synthetic activities of the polymerase (i.e., initiation and polymerization), and that it is involved particularly in the metal binding associated with the dNTP site.