Fig 2. Invertible regions are present in the hsd locus encoding a Type I restriction modification system found in L. monocytogenes CC8 strains.

The figure shows the four different configurations of the hsd locus, denoted variants A through D as indicated on the left, which were generated through site-specific gene shuffling. Within each DNA sequence recognition (specificity) gene (hsdS), the segments encoding each target recognition domain are shown as hexagonal boxes, in which identical colouring represents identical domains. The inverted repeat sequences are shown at the top, with arrows pointing to their location within the hsdS genes. Dotted lines drawn between two hsd locus variants illustrate the DNA inversion event required for transition between the two configurations. The locus corresponds to genes LMR479A_0528 to LMR479A_0532 in strain R479a, which are inserted between genes corresponding to lmo0520-lmo0521 in L. monocytogenes EGD-e.