High level synthesis in Escherichia coli of the Bacillus subtilis phage phi 29 proteins p3 and p4 under the control of phage lambda PL promoter.

The Hind III G fragment from the Bacillus subtilis phage phi 29 DNA, inserted downstream from the bacteriophage lambda promoter PL carried by a pBR322 derivative plasmid (pPLc28), directed the synthesis in E. coli of two proteins of apparent molecular weight 27500 and 12500. With the use of the recombinants obtained with the DNA from mutants sus3(91) and sus4(56), the two proteins were identified as a modified p3 (p3'), the protein covalently linked to the 5' ends of phi 29 DNA, and p4, responsible for the phi 29 late transcription, respectively. Under the best conditions used, proteins p4 and p3' were produced in E. coli from the cloned DNA fragments in an amount corresponding to approximately 30% and 6% of total de novo protein synthesis, respectively.