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Conformational Switch Regulates the DNA Cytosine Deaminase Activity of Human APOBEC3B.

Scientific reports | 2017

The APOBEC3B (A3B) single-stranded DNA (ssDNA) cytosine deaminase has important roles in innate immunity but is also a major endogenous source of mutations in cancer. Previous structural studies showed that the C-terminal catalytic domain of human A3B has a tightly closed active site, and rearrangement of the surrounding loops is required for binding to substrate ssDNA. Here we report structures of the A3B catalytic domain in a new crystal form that show alternative, yet still closed, conformations of active site loops. All-atom molecular dynamics simulations support the dynamic behavior of active site loops and recapitulate the distinct modes of interactions that maintain a closed active site. Replacing segments of A3B loop 1 to mimic the more potent cytoplasmic deaminase APOBEC3A leads to elevated ssDNA deaminase activity, likely by facilitating opening of the active site. These data collectively suggest that conformational equilibrium of the A3B active site loops, skewed toward being closed, controls enzymatic activity by regulating binding to ssDNA substrates.

Pubmed ID: 29234087 RIS Download

Research resources used in this publication

None found

Antibodies used in this publication

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Associated grants

  • Agency: NCRR NIH HHS, United States
    Id: S10 RR029205
  • Agency: NIGMS NIH HHS, United States
    Id: R01 GM118000
  • Agency: NIGMS NIH HHS, United States
    Id: P41 GM103403
  • Agency: NCI NIH HHS, United States
    Id: R21 CA206309
  • Agency: NIGMS NIH HHS, United States
    Id: P41 GM103426
  • Agency: NIH HHS, United States
    Id: DP2 OD007237
  • Agency: NIGMS NIH HHS, United States
    Id: R35 GM118047
  • Agency: Howard Hughes Medical Institute, United States

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