This compaction is also characterized by the rotation of one ring relative to another (Figure 4Bii; indicated with the tilted green dotted line). While previously determined ADEP-ClpP structures adopting the extended conformation have led to the hypothesis that ADEP bindingconstrains ClpP in its active, extended conformation, the structure of the ADEP-28−HsClpP complex being in the compact conformation provides the first structural basis demonstrating that the ADEP−ClpP complex is in fact structurally dynamic and is able to sample through multipleconformational states over its catalytic cycle.