Identification, cloning, and characterization of the bacteriophage N4 gene encoding the single-stranded DNA-binding protein. A protein required for phage replication, recombination, and late transcription.

The coliphage N4-coded single-stranded DNA-binding protein (N4SSB) is essential for phage replication and for expression of the phage late genes, which are transcribed by the Escherichia coli sigma 70 RNA polymerase. As a first step in investigating the role of N4SSB in replication and transcriptional activation, we have identified and sequenced the N4SSB gene. The gene encodes a 265-amino acid protein with no apparent sequence homology to other single-stranded DNA-binding proteins. We present data indicating that N4SSB is also essential for phage recombination. Mutational analysis of the carboxyl terminus of the protein indicates that this region is required for protein-protein interactions with the N4 replication, N4 recombination, and E. coli transcriptional machineries, while the rest of the protein contains the determinants for single-stranded DNA binding.