The dimeric SOS mutagenesis protein UmuD is active as a monomer.
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.
Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115, USA.
Jaylene N
JN
Ollivierre
Jacquelyn L
JL
Sikora
Penny J
PJ
Beuning
D019943:Amino Acid Substitution; D002470:Cell Survival; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D016296:Mutagenesis / Q000528:radiation effects; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D055503:Protein Multimerization; D055550:Protein Stability; D013014:SOS Response, Genetics
D029968:Escherichia coli Proteins; D050505:Mutant Proteins; D004259:DNA-Directed DNA Polymerase; C055218:UmuD protein, E coli