The dimeric SOS mutagenesis protein UmuD is active as a monomer

J Biol Chem. 2011 Feb 4;286(5):3607-17. doi: 10.1074/jbc.M110.167254. Epub 2010 Nov 29.


The homodimeric umuD gene products play key roles in regulating the cellular response to DNA damage in Escherichia coli. UmuD(2) is composed of 139-amino acid subunits and is up-regulated as part of the SOS response. Subsequently, damage-induced RecA·ssDNA nucleoprotein filaments mediate the slow self-cleavage of the N-terminal 24-amino acid arms yielding UmuD'(2). UmuD(2) and UmuD'(2) make a number of distinct protein-protein contacts that both prevent and facilitate mutagenic translesion synthesis. Wild-type UmuD(2) and UmuD'(2) form exceptionally tight dimers in solution; however, we show that the single amino acid change N41D generates stable, active UmuD and UmuD' monomers that functionally mimic the dimeric wild-type proteins. The UmuD N41D monomer is proficient for cleavage and interacts physically with DNA polymerase IV (DinB) and the β clamp. Furthermore, the N41D variants facilitate UV-induced mutagenesis and promote overall cell viability. Taken together, these observations show that a monomeric form of UmuD retains substantial function in vivo and in vitro.

Publication types

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

MeSH terms

  • Amino Acid Substitution
  • Cell Survival
  • DNA-Directed DNA Polymerase / genetics
  • DNA-Directed DNA Polymerase / metabolism*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Mutagenesis* / radiation effects
  • Mutant Proteins / chemistry
  • Mutant Proteins / metabolism
  • Protein Multimerization*
  • Protein Stability
  • SOS Response, Genetics


  • Escherichia coli Proteins
  • Mutant Proteins
  • DNA-Directed DNA Polymerase
  • UmuD protein, E coli