Nucleotide sequence from the ssRNA bacteriophage JP34 resolves the discrepancy between serological and biophysical classification

The nucleotide sequence of the coat and lysis genes of the single-stranded RNA bacteriophage JP34 is presented. Serological inactivation studies classified this phage as an intermediate between groups I and II. We show that the nucleotide similarity with group I is less than 45% but more than 95% for group II, classifying JP34 as a member of group II. The altered serotype of JP34 is most likely due to the change of three critical amino acids of the coat protein to residues present in group I phage MS2 at the homologous positions. Serological characterization of RNA bacteriophages is thus not unambiguous. Phylogenetic sequence comparison between JP34, GA, and MS2 confirms the existence of a conserved helix in the coat gene of group I and group II phages. We also show that the JP34 coat and lysis genes can be expressed in cDNA clones and that the translation of the lysis gene is coupled to coat gene translation analogous to the regulation found in the group I phages.