Cleavage and circularization of single-stranded DNA: a novel enzymatic activity of phi X174 A* protein.
Purified phi X gene A* protein cleaves phi X single stranded DNA. The cleavage appears to be stoichiometric, whereby a gene A* protein molecule cleaves a phosphodiester bond and binds to the DNA fragment. The size of the cleavage product was inversely proportional to the ratio of A* protein to DNA in the reaction mixture. The cleavage of the DNA resulted in the formation of an A* protein - ssDNA complex identified on SDS-polyacrylamide gels and by banding in CsCl. An A* protein-ssDNA complex was isolated by gel filtration and shown to be active in a ligating reaction in which the two ends of the DNA fragment were joined to form a covalently closed circle. The joining reaction required Mg++ ions and was accompanied by the release of the protein from the DNA.
D010584:Bacteriophage phi X 174 / Q000201:enzymology*; D011088:DNA Ligases / Q000378:metabolism; D004270:DNA, Circular / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism*; D003852:Deoxyribonucleoproteins / Q000302:isolation & purification / Q000378:metabolism; D011485:Protein Binding; D014764:Viral Proteins / Q000302:isolation & purification / Q000378:metabolism*
D004270:DNA, Circular; D004277:DNA, Single-Stranded; D003852:Deoxyribonucleoproteins; D014764:Viral Proteins; D011088:DNA Ligases