Overproduction and purification of protein p6 of Bacillus subtilis phage ø29

A ø29 DNA fragment containing gene 6, required for DNA replication, has been cloned in plasmid pPLc28 under the control of the PL promoter of phage lambda. A polypeptide with an electrophoretic mobility close to that of p6 was labelled with 35S methionine after heat induction. This protein, representing about 4% of the total E. coli protein after 1 h of induction, was obtained in a highly purified form. The protein was characterized as p6 by amino acid analysis and NH2 COOH-terminal sequence determination. Protein p6 has an apparent molecular weight of 23,600 suggesting that the native form of the protein is a dimer. The purified protein p6 stimulated the protein-primed initiation of ø29-coded DNA replication when added to purified proteins p2 (ø29-coded DNA polymerase) and p3 (terminal protein).Peer reviewe