Molecular simulations reveal a common binding mode for glycosylase binding of oxidatively damaged DNA lesions

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Cellular DNA faces constant oxidative stress from internal and external sources.
• Oxidative DNA damage, particularly 8-oxo-guanine (8OG) and FapydG, contributes to aging and diseases like cancer.
• The DNA glycosylase Fpg in Escherichia coli repairs both 8OG and FapydG lesions.

Purpose of the Study:

• To investigate the structural basis for differential binding of 8OG and FapydG in the Fpg active site.
• To understand the role of specific amino acid residues in modulating lesion recognition and binding.
• To explore how sequence variations in Fpg affect DNA repair outcomes.

Main Methods:

• Utilized X-ray crystallography to determine the structures of Fpg with bound 8OG and FapydG.
• Performed molecular dynamics simulations to analyze the binding modes and conformational dynamics of the lesions in the Fpg active site.
• Compared simulations using thermophilic Fpg sequences with non-conserved E77 to those with consensus S77.

Main Results:

• X-ray crystallography revealed distinct conformations of 8OG and FapydG within the Fpg active site.
• Simulations indicated that the non-conserved E77 residue in thermophilic Fpg influences the differential binding of 8OG and FapydG.
• In simulations with a consensus S77 residue, both lesions adopted highly similar binding modes.

Conclusions:

• The differential binding of 8OG and FapydG by Fpg is significantly influenced by the presence of residue E77.
• Sequence variations in DNA repair enzymes can alter their substrate specificity and binding dynamics.
• Understanding these molecular mechanisms is crucial for comprehending DNA repair fidelity and preventing diseases associated with DNA damage.