Understanding the coupling between DNA damage detection and UvrA's ATPase using bulk and single molecule kinetics

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Nucleotide excision repair (NER) is crucial for cellular defense against DNA damage, particularly from UV radiation.
• In Escherichia coli, UvrA and UvrB are key enzymes in DNA damage recognition.
• The precise function of UvrA's two ATPase domains in NER remains unclear.

Purpose of the Study:

• To elucidate the role of nucleotide binding in the kinetic cycle of UvrA.
• To investigate how DNA damage influences UvrA's ATPase activity and DNA binding.
• To understand the coupling between DNA damage detection and UvrA's ATPase function.

Main Methods:

• Employed single-molecule fluorescence microscopy.
• Utilized classic biochemical methods, including steady-state ATPase activity measurements.
• Analyzed UvrA's DNA binding kinetics under various nucleotide conditions and DNA damage states.

Main Results:

• UvrA's ATPase activity is stimulated upon DNA binding.
• UV-damaged DNA did not alter steady-state ATPase activity, but significantly increased UvrA's attached lifetime in the presence of ATP.
• Both UV damage and nucleotide cofactors influence UvrA's DNA-bound lifetime.

Conclusions:

• UvrA likely employs negative cooperativity between its ATPase sites, regulated by damage recognition.
• The second ATPase site activation appears to be sequential and damage-dependent.
• This mechanism highlights the intricate coupling of DNA damage detection and enzymatic activity in UvrA.