Transfecting deoxyribonucleic acid of Bacillus bacteriophage phi 29 that is protease sensitive.

The transfecting activity of Bacillus phage varphi29 DNA, extracted either by sodium lauroyl sarcosine-phenol or by 2 M perchlorate, was destroyed by treatment with proteolytic enzymes, although these enzymes did not effect transfecting DNAs of SPP1, SPO1, and SP50. These facts suggest that a protein is associated with transfective varphi29 DNA. Stabilization of protease-resistance during transfection appeared earlier than that of DNaseresistance, indicating that the protein associated with varphi29 DNA is necessary for initiation of the incorporation of DNA molecules into competent cells. The physical nature of varphi29 DNA before and after the trypsin treatment was investigated by sucrose and CsCl density gradient centrifugations. The trypsin treatment did not alter the sedimentation rate of the unit varphi29 DNA; however, it did convert the sedimentation rate of the aggregated material in the untreated DNA to that of the unit varphi29 DNA. The density of the trypsinized DNA was 0.009 g/cm(3) greater than that of the untreated DNA. The possible location of the protein on the DNA is discussed.