Subunit-specific degradation of the UmuD/D' heterodimer by the ClpXP protease: the role of trans recognition in UmuD' stability

EMBO J. 2000 Oct 2;19(19):5251-8. doi: 10.1093/emboj/19.19.5251.


The Escherichia coli UmuD' protein is a subunit of the recently described error-prone DNA polymerase, pol V. UmuD' is initially synthesized as an unstable and mutagenically inactive pro-protein, UmuD. Upon processing, UmuD' assumes a relatively stable conformation and becomes mutagenically active. While UmuD and UmuD' by themselves exist in vivo as homodimers, when together they preferentially interact to form heterodimers. Quite strikingly, it is in this context that UmuD' becomes susceptible to ClpXP-mediated proteolysis. Here we report a novel targeting mechanism designed for degrading the mutagenically active UmuD' subunit of the UmuD/D' heterodimer complex, while leaving the UmuD protein intact. Surprisingly, a signal that is essential and sufficient for targeting UmuD' for degradation was found to reside on UmuD not UmuD'. UmuD was also shown to be capable of channeling an excess of UmuD' to ClpXP for degradation, thereby providing a mechanism whereby cells can limit error-prone DNA replication.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphatases / chemistry*
  • Amino Acid Sequence
  • Bacterial Proteins / chemistry*
  • DNA Replication
  • DNA-Directed DNA Polymerase / chemistry*
  • Dimerization
  • Endopeptidase Clp
  • Enzyme Stability
  • Escherichia coli / chemistry*
  • Escherichia coli Proteins*
  • Molecular Sequence Data
  • Mutagenesis
  • Serine Endopeptidases / chemistry*


  • Bacterial Proteins
  • Escherichia coli Proteins
  • DNA polymerase V, E coli
  • DNA-Directed DNA Polymerase
  • UmuD protein, E coli
  • Serine Endopeptidases
  • ClpXP protease, E coli
  • Endopeptidase Clp
  • Adenosine Triphosphatases