High-resolution crystal structures reveal plasticity in the metal binding site of apurinic/apyrimidinic endonuclease i

Hongzhen He, Qiujia Chen, Millie Georgiadis

Research output: Contribution to journalArticle

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Abstract

Apurinic/apyrimidinic endonuclease I (APE1) is an essential base excision repair enzyme that catalyzes a Mg2+-dependent reaction in which the phosphodiester backbone is cleaved 5′ of an abasic site in duplex DNA. This reaction has been proposed to involve either one or two metal ions bound to the active site. In the present study, we report crystal structures of Mg2+, Mn2+, and apo-APE1 determined at 1.4, 2.2, and 1.65 Å, respectively, representing two of the highest resolution structures yet reported for APE1. In our structures, a single well-ordered Mn2+ ion was observed coordinated by D70 and E96; the Mg2+ site exhibited disorder modeled as two closely positioned sites coordinated by D70 and E96 or E96 alone. Direct metal binding analysis of wild-type, D70A, and E96A APE1, as assessed by differential scanning fluorimetry, indicated a role for D70 and E96 in binding of Mg2+ or Mn2+ to APE1. Consistent with the disorder exhibited by Mg2+ bound to the active site, two different conformations of E96 were observed coordinated to Mg2+. A third conformation for E96 in the apo structure is similar to that observed in the APE1-DNA-Mg2+ complex structure. Thus, binding of Mg2+ in three different positions within the active site of APE1 in these crystal structures corresponds directly with three different conformations of E96. Taken together, our results are consistent with the initial capture of metal by D70 and E96 and repositioning of Mg2+ facilitated by the structural plasticity of E96 in the active site.

Original languageEnglish
Pages (from-to)6520-6529
Number of pages10
JournalBiochemistry
Volume53
Issue number41
DOIs
StatePublished - Oct 21 2014

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DNA-(Apurinic or Apyrimidinic Site) Lyase
Endonucleases
Plasticity
Conformations
Catalytic Domain
Crystal structure
Metals
Binding Sites
Deoxyribonuclease I
DNA
Ions
Fluorometry
Metal ions
Repair
DNA Repair
Scanning
Enzymes

ASJC Scopus subject areas

  • Biochemistry
  • Medicine(all)

Cite this

High-resolution crystal structures reveal plasticity in the metal binding site of apurinic/apyrimidinic endonuclease i. / He, Hongzhen; Chen, Qiujia; Georgiadis, Millie.

In: Biochemistry, Vol. 53, No. 41, 21.10.2014, p. 6520-6529.

Research output: Contribution to journalArticle

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abstract = "Apurinic/apyrimidinic endonuclease I (APE1) is an essential base excision repair enzyme that catalyzes a Mg2+-dependent reaction in which the phosphodiester backbone is cleaved 5′ of an abasic site in duplex DNA. This reaction has been proposed to involve either one or two metal ions bound to the active site. In the present study, we report crystal structures of Mg2+, Mn2+, and apo-APE1 determined at 1.4, 2.2, and 1.65 {\AA}, respectively, representing two of the highest resolution structures yet reported for APE1. In our structures, a single well-ordered Mn2+ ion was observed coordinated by D70 and E96; the Mg2+ site exhibited disorder modeled as two closely positioned sites coordinated by D70 and E96 or E96 alone. Direct metal binding analysis of wild-type, D70A, and E96A APE1, as assessed by differential scanning fluorimetry, indicated a role for D70 and E96 in binding of Mg2+ or Mn2+ to APE1. Consistent with the disorder exhibited by Mg2+ bound to the active site, two different conformations of E96 were observed coordinated to Mg2+. A third conformation for E96 in the apo structure is similar to that observed in the APE1-DNA-Mg2+ complex structure. Thus, binding of Mg2+ in three different positions within the active site of APE1 in these crystal structures corresponds directly with three different conformations of E96. Taken together, our results are consistent with the initial capture of metal by D70 and E96 and repositioning of Mg2+ facilitated by the structural plasticity of E96 in the active site.",
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