Molecular Determinants of MecA as a Degradation Tag for the ClpCP Protease

Ziqing Mei,Feng Wang,Yutao Qi,Zhiyuan Zhou,Qi Hu,Han Li,Jiawei Wu,Yigong Shi

doi:10.1074/jbc.m109.053017

Abstract

Regulated proteolysis by ATP-dependent proteases is universal in all living cells. In Bacillus subtilis, the degradation of the competence transcription factor ComK is mediated by a ternary complex involving the adaptor protein MecA and the ATP-dependent protease ClpCP. Here we demonstrate that a C-terminal, 98-amino acid domain of MecA (residues 121-218) serves as a non-recycling, degradation tag and targets a variety of fusion proteins to the ClpCP protease for degradation. MecA-(121-218) facilitates productive oligomerization of ClpC, stimulates the ATPase activity of ClpC, and allows the activated ClpC complex to stably associate with ClpP. Importantly, the ClpCP protease undergoes dynamic cycles of assembly and disassembly, which are triggered by association with MecA and the degradation of MecA, respectively.

Highlights

ClpA, ClpC, and ClpX belong to the conserved Hsp100/Clp family of AAAϩ ATPases, each of which forms a hexameric assembly in its active form [11]
MecA is required for activation of the ClpCP protease, it is degraded along with the substrate protein ComK [28]
Mechanism of the MecA-ClpCP Protease sequences in MecA that are required for subsequent degradation of MecA by the ClpCP protease? Are these two sets of minimal sequences the same? Fourth, can MecA serve as a degradation tag for other proteins in a way that is reminiscent of SsrA? Last but not least, how does the structure of MecA support its function?

Summary

Introduction

ClpA, ClpC, and ClpX belong to the conserved Hsp100/Clp family of AAAϩ ATPases, each of which forms a hexameric assembly in its active form [11]. MecA is required for activation of the ClpCP protease, it is degraded along with the substrate protein ComK [28]. An additional flexible sequence of at least 9 amino acids is required for this degradation tag to be degraded by the assembled ClpCP protease.

Results

Conclusion