Purification and properties of bacteriophage phi X 174 gene D product

Abstract

Bacteriophage phi X 174 gene D product, a protein required for single-stranded DNA synthesis by the phage, has been purified to near homogeneity. The protein is very abundant; approximately 10(5) monomers are present per infected cell when lysis is delayed. The protein has a monomer molecular weight of 15,200 and is normally a tetramer; however, it can form very large aggregates at high concentrations. Amino acid analysis shows an excess of arginine over lysine and a relatively high number of nonpolar residues. The protein carries a net negative charge at neutral pH. The first eight amino acids of the protein sequence have been determined; they are Ser-Gln-Val-Thr-Glu-Gln-Arg-Val. The carboxy-terminal residue is methionine. The protein has not yet been shown to bind directly to any single-stranded DNA; it does not adsorb to denatured calf thymus DNA-cellulose.