FIG. 4.

(A) Sequence of φ31 DNA from the beginning of ORF cI through the beginning of ORF 238, showing the divergent promoters P1 and P2 and the putative operator sites of the regulatory region (O₁, O₂, and O₃). The three putative operator sites are shaded. Arrows show the promoters P1 and P2, and the −10 and −35 sequences are underlined. A bent arrow indicates the transcriptional start site located downstream of P1. Potential ribosome binding sites are in bold lowercase letters. (B) Alignment of the half-sites of the three operator regions of phage φ31. Conserved bases in the consensus sequence are shown with capital letters.