An Escherichia coli replication protein that recognizes a unique sequence within a hairpin region in phi X174 DNA.

Protein n', a prepriming DNA replication enzyme of Escherichia coli, is a phi X174 DNA-dependent ATPase. Restriction of phi X174 DNA have led to the identification of a 55-nucleotide fragment that carries the protein n' recognition sequence. Molecular hybridization and sequence analysis have 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 led to the start of phi X174 complementary DNA strand replication.