Abstract
Protein n'', a prepriming DNA replication enzyme of E. coli, is a .vphi.X174 DNA-dependent ATPase. Restriction endonuclease fragmentation and exonuclease VII digestion of .vphi.X174 DNA led to the identification of a 55-nucleotide fragment that carries the protein n'' recognition sequence. Molecular hybridization and sequence analysis located this sequence within the untranslated region between genes F and G, a map location analogous to that of the unique complementary strand origin of phage G4 DNA. Within the 55-nucleotide fragment is a sequence of 44 nucleotides that forms a stable hairpin structure. This duplex may be the signal for protein n'' to initiate the prepriming events that lead to the start of .vphi.X174 complementary DNA strand replication.