Cullin-RING ubiquitin ligases (CRLs) comprise an extensive class of multisubunit enzymes, which promote the ubiquitylation and degradation of a large number of protein substrates. CRLs uniquely exploit combinatorial diversity in order to achieve their unparalleled versatility. Conserved core complexes organized around a Cullin (CUL)-like protein—up to eight exist in humans—associate with hundreds of different substrate receptors. Since receptors are known to seek out multiple substrates, the total number of CRL targets is likely in the thousands, predicting that CRLs may impact virtually any cellular process. Actin-based motility is the most recent addition to this repertoire, as shown in a report by Chen et al. in this issue of Molecular Cell (Chen et al., 2009).