Summary information and primary citation
- PDB-id
-
6cvp;
DSSR-derived features in text and
JSON formats
- Class
- hydrolase-DNA-RNA
- Method
- X-ray (1.999 Å)
- Summary
- Human aprataxin (aptx) r199h bound to RNA-DNA, amp and
zn product complex
- Reference
-
Tumbale P, Schellenberg MJ, Mueller GA, Fairweather E,
Watson M, Little JN, Krahn J, Waddell I, London RE,
Williams RS (2018): "Mechanism
of APTX nicked DNA sensing and pleiotropic inactivation
in neurodegenerative disease." EMBO J.,
37. doi: 10.15252/embj.201798875.
- Abstract
- The failure of DNA ligases to complete their catalytic
reactions generates cytotoxic adenylated DNA strand breaks.
The APTX RNA-DNA deadenylase protects genome integrity and
corrects abortive DNA ligation arising during
ribonucleotide excision repair and base excision DNA
repair, and <i>APTX</i> human mutations cause
the neurodegenerative disorder ataxia with oculomotor
ataxia 1 (AOA1). How APTX senses cognate DNA nicks and is
inactivated in AOA1 remains incompletely defined. Here, we
report X-ray structures of APTX engaging nicked RNA-DNA
substrates that provide direct evidence for a
wedge-pivot-cut strategy for 5'-AMP resolution shared with
the alternate 5'-AMP processing enzymes POLβ and FEN1. Our
results uncover a DNA-induced fit mechanism regulating APTX
active site loop conformations and assembly of a
catalytically competent active center. Further, based on
comprehensive biochemical, X-ray and solution NMR results,
we define a complex hierarchy for the differential impacts
of the AOA1 mutational spectrum on APTX structure and
activity. Sixteen AOA1 variants impact APTX protein
stability, one mutation directly alters deadenylation
reaction chemistry, and a dominant AOA1 variant
unexpectedly allosterically modulates APTX active site
conformations.
