The Dimeric SOS Mutagenesis Protein UmuD Is Active as a Monomer

• Published in: The Journal of biological chemistry 2011-02, Vol.286 (5), p.3607-3617
• Main Authors: Ollivierre, Jaylene N., Sikora, Jacquelyn L., Beuning, Penny J.
• Format: Article
• Language: English
• Subjects: Amino Acid Substitution; Cell Survival; DinB; DNA Damage; DNA Polymerase; DNA-Directed DNA Polymerase - genetics; DNA-Directed DNA Polymerase - metabolism; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Mutagenesis - radiation effects; Mutagenesis Mechanisms; Mutant Proteins - chemistry; Mutant Proteins - metabolism; Protein Conformation; Protein Multimerization; Protein Stability; Protein Structure and Folding; SOS Response; SOS Response, Genetics; Translesion DNA Synthesis; UmuD; β Clamp
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M110.167254

The homodimeric umuD gene products play key roles in regulating the cellular response to DNA damage in Escherichia coli. UmuD2 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. UmuD2 and UmuD′2 make a number of distinct protein-protein contacts that both prevent and facilitate mutagenic translesion synthesis. Wild-type UmuD2 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.