Objective    To investigate the binding ability to specific DNA sequence of the putative small subunit of the terminase of Pseudomonas aeruginosa bacteriophage PaP3.     Methods    The fragment of pap3p01 was amplified from the genome of bacteriophage PaP3 and cloned into expression plasmid pQE31. The recombinant vector pQE31-PaP3p01 was transformed to E. coli JM109. After induction with IPTG

the expressed bacteria was dissolved with lysis buffer

then the tagged protein was purified by Ni-NTA affinity chromatography. The DNA fragment carrying the putative small subunit binding site was gained by PCR and restrictive enzyme digestion

and marked with biotin in 3′-end

finally the DNA-binding ability of the fusion protein H6-PaP3P01 was determined by EMSA.     Results    The expression plasmid pQE31-PaP3p01 was successfully constructed. The fusion protein H6-PaP3P01 was highly expressed and in the suspended layer. After purified by Ni-NTA affinity chromatography and desalted

the H6-PaP3P01 protein can bind to the specific DNA fragment.     Conclusion    The fusion protein H6-PaP3P01 was successfully expressed and purified

and it has the specific DNA-binding activity. Our present work lays the foundation for the further research of packaging mechanism of bacteriophage PaP3.