Figure 1.

Domain architectures of yeast Mec1-Ddc2 and Tel1. Ddc2 is an integral partner of the Mec1-Ddc2 complex. Similar colors indicate analogous regions between Mec1 and Tel1. Part of the C-lobe region of the kinase domains is expanded to highlight critical regions that play a role in the activation mechanism (discussed in text). The PRD-I (PIKK Regulatory Domain - Insertion) (dark green) varies in size between PIKK members; it plays an important role in auto-inhibiting and/or restricting substrate access to the kinase active site. Residue numbers of S. cerevisiae Mec1-Ddc2 and Tel1 are shown.