Fig. 4.

Group 1 sRNAs are a family of highly conserved, phage-derived transcripts. Regions 2 and 3 from Group 1 sRNAs were isolated and an alignment created, uncovering strong similarity to the C4 RNA of phages P1 and P7. Folding predictions demonstrated that all but three transcripts (ABUWs047, ABUWs067 and ABUWs069; highlighted in red) show characteristic structural features of the C4 molecule; consisting of three stems and three loops (termed the tetraloop, loop a′ and loop b′). For the phage molecules, divergent residues between P1 and P7 are shown in red.