Figure 10.

The target recognition domain of the S subunit, which binds to the DNA target sequence AAC (34), and the catalytic domain of the M subunit, which recognises the methylation state of this target, are shown in grey and blue space-filling representations, respectively. The ocr monomer shown in red is placed onto this partial model of EcoKI guided by the superimposition of DNA molecules derived from Figure 9. The second ocr monomer is shown as a white ribbon to define the orientation of ocr and EcoKI. Highlighted in yellow on the ocr monomer are mutation sites not covered by the modelled domains of EcoKI. These locations must be covered by other parts of EcoKI to explain the protection from acrylamide quenching when EcoKI is bound to ocr.