Abstract
Repair of DNA damage relies on various pathways including the base excision repair (BER) which targets erroneous bases in the DNA. Here, Uracil-DNA glycosylases (UDGs) are responsible for recognition and removal of uracil base from the DNA. Here, we characterize the interaction of Staphylococcus aureus UDG (SAUDG) with a naturally occurring variant of S. aureus uracil-DNA glycosylase inhibitor (SAUGI). This variant contains a histidine instead of a glutamate at the 24th position which affects the SAUDG:SAUGI interaction surface. We assessed the complex formation of SAUDG with these two SAUGI variants by independent biophysical methods. Our data reveal that the residue difference at the 24th position does not have a marked effect on the binding affinity, yet it confers alteration of the thermodynamics of the interaction. We propose that the E24H variant of SAUGI allows efficient complex formation, and consequently, inhibition of SAUDG.
Highlights
Appearance of uracil in DNA, either as a result of cytosine deamination or erroneous nucleotide incorporation of DNA polymerases, usually a mistake that needs to be excised [1]
We focused on one of the naturally occurring residue variation of the S. aureus uracil-DNA glycosylase inhibitor (SAUGI) proteins encoded by different Staphylococcal strains
SAUGIE24H variants were first assessed by Microscale thermophoresis (MST) (Fig. 1)
Summary
Appearance of uracil in DNA, either as a result of cytosine deamination or erroneous nucleotide incorporation of DNA polymerases, usually a mistake that needs to be excised [1]. The base excision repair pathway (BER) corrects DNA base damages arising e.g. from oxidation, deamination or alkylation. As the initial step in BER, the damaged or mismatched base is recognized by a DNA glycosylase. Uracil-DNA glycosylase (UDG) employs a nucleotide-flipping mechanism in which the target uracil is extruded out of the DNA double helix and recognized by the active site of the enzyme, where catalysis takes place. Glycosylase action leaves an abasic site that is further processed by short-patch repair or long-patch repair mechanisms that use largely different enzymes [5, 6]. The abasic site that is removed by a 5’-acting apurinic/apyrimidinic (AP) endonuclease and a deoxyribophosphodiesterase (dRpase), leaving a gap that is filled by DNA polymerase and closed by DNA ligase [7]
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