An Adaptor Hierarchy Regulates Proteolysis during a Bacterial Cell Cycle

Regulated protein degradation is essential. The timed destruction of crucial proteins by the ClpXP protease drives cell-cycle progression in the bacterium Caulobacter crescentus. Although ClpXP is active alone, additional factors are inexplicably required for cell-cycle-dependent proteolysis. Here, we show that these factors constitute an adaptor hierarchy wherein different substrates are destroyed based on the degree of adaptor assembly. The hierarchy builds upon priming of ClpXP by the adaptor CpdR, which promotes degradation of one class of substrates and also recruits the adaptor RcdA to degrade a second class of substrates. Adding the PopA adaptor promotes destruction of a third class of substrates and inhibits degradation of the second class. We dissect RcdA to generate bespoke adaptors, identifying critical substrate elements needed for RcdA recognition and uncovering additional cell-cycle-dependent ClpXP substrates. Our work reveals how hierarchical adaptors and primed proteases orchestrate regulated proteolysis during bacterial cell-cycle progression. [Display omitted] •Protease selectivity during cell cycle is defined by a hierarchy of adaptors•Priming of the ClpXP protease by CpdR is needed for adaptor recruitment•RcdA is an adaptor that binds multiple substrates and additional adaptors•Which substrates are degraded depends on the degree of adaptor assembly Protein degradation during the Caulobacter cell cycle relies on an adaptor hierarchy. Priming of the protease by one adaptor recruits additional adaptors, and substrate degradation occurs based on the degree of adaptor assembly.