Nucleotide sequence and genome organization of bacteriophage S13 DNA.

The complete sequence of bacteriophage S13 DNA has been determined. The molecule has 5386 nucleotides and differs from phi X174 by 87 transitions and 24 transversions. All the proteins, A,A*,B,C,D,E,F,G,H, J and K found in phi X174 are also present in S13. Due to changes in the H/A intergenic region of S13, the start of an additional protein, A', has been identified. Genes F and H coding for the capsid and spike proteins, respectively, are the least conserved in comparison to phi X174. Many of the silent changes, as well as some amino acid changes, are found in the same nucleotide sequence positions in phage G4, confirming the interrelationship between the three phages.