Figure 1.

(a) Arrangement of the AhdI R-M genes. The M and S genes, and the C and R genes are arranged convergently, with transcription in the direction shown. The two operons are separated by a central self-complementary region, depicted here as a hairpin. (b) Secondary structure prediction. The amino acid sequence of C.AhdI is given with the putative helix–turn–helix region underlined. Secondary structure predictions are shown from the program PSIPRED with associated reliability indices (Rel) on a scale of 1–10. Predicted helices are denoted as ‘H’.