Heterodimer formation in the DNA damage response protein UmuD

Abstract

DNA damage is universal and all organisms have systems in place to respond to such damage. The Escherichia coli umuD gene products are essential to SOS-induced mutagenesis in response to DNA damage. UmuD is a dynamic 139-amino acid homodimeric protein that binds to a RecA/ssDNA nucleoprotein filament, which stimulates the latent ability of UmuD to cleave its N-terminal 24 amino acids to form UmuD′. UmuD and UmuD′ have been shown to perform distinct functions in both preventing and facilitating mutagenesis. The umuD gene products are highly dynamic proteins. Through the use of models and structural data, it was concluded that structural rearrangement of UmuD occurs upon binding to the RecA filament and upon cleavage. It has been proposed that the UmuD′D heterodimer is the predominant conformer of the umuD gene products. We are designing mutations at the dimer interface of UmuD that will allow us to determine the kinetics of dimer exchange as well as of heterodimer formation. The goal of our research is to determine the conformation and dynamics of the umuD gene products in order to understand how their protein-protein interactions regulate cellular responses to DNA damage. Research supported by NSF Career MCB-0845033.