Sequence determinants of MecA for ClpCP-mediated degradation of ComK and MecA. A, characterization of deletion variants of MecA. The full-length MecA and the substrate protein ComK were degraded by the ClpCP protease (lanes 4–6). Removal of the N-terminal 77 amino acids in MecA led to complete abrogation of ComK degradation but had no impact on MecA degradation. Further removal of the linker sequence 78–120 resulted in abolishment of MecA degradation. All SDS-PAGE gels in this study were visualized by Coomassie Brilliant Blue staining. The asterisks indicate the position of pyruvate kinase. The MecA variants are indicated by black dots. MecA78 denotes MecA-(78–218), MecA121 denotes MecA-(121–218), and so on. B, the linker sequence 78–120 is not required for MecA degradation. Removal of amino acids 78–96, 96–120, or 78–120 from the full-length MecA protein still allowed the degradation of the cognate MecA variants. C, replacement of the linker sequence 78–120 by a flexible sequence from EGL-1 allowed efficient degradation of the fusion protein between EGL-1 and MecA-(121–218).