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Disease-associated mutations inactivate AMP-lysine hydrolase activity of Aprataxin
Journal article   Open access   Peer reviewed

Disease-associated mutations inactivate AMP-lysine hydrolase activity of Aprataxin

Heather F Seidle, Pawel Bieganowski and Charles Brenner
The Journal of biological chemistry, Vol.280(22), pp.20927-20931
06/03/2005
DOI: 10.1074/jbc.M502889200
PMCID: PMC2556069
PMID: 15790557
url
https://doi.org/10.1074/jbc.M502889200View
Published (Version of record) Open Access

Abstract

Ataxia-oculomotor apraxia syndrome 1 is an early onset cerebellar ataxia that results from loss of function mutations in the APTX gene, encoding Aprataxin, which contains three conserved domains. The forkhead-associated domain of Aprataxin mediates protein-protein interactions with molecules that respond to DNA damage, but the cellular phenotype of the disease does not appear to be consistent with a major loss in DNA damage responses. Disease-associated mutations in Aprataxin target a histidine triad domain that is similar to Hint, a universally conserved AMP-lysine hydrolase, or truncate the protein NH2-terminal to a zinc finger. With novel fluorigenic substrates, we demonstrate that Aprataxin possesses an active-site-dependent AMP-lysine and GMP-lysine hydrolase activity that depends additionally on the zinc finger for protein stability and on the forkhead associated domain for enzymatic activity. Alleles carrying any of eight recessive mutations associated with ataxia and oculomotor apraxia encode proteins with huge losses in protein stability and enzymatic activity, consistent with a null phenotype. The mild presentation allele, APTX-K197Q, associated with ataxia but not oculomotor apraxia, encodes a protein with a mild defect in stability and activity, while enzyme encoded by the atypical presentation allele, APTX-R199H, retained substantial function, consistent with altered and not loss of activity. The data suggest that the essential function of Aprataxin is reversal of nucleotidylylated protein modifications, that all three domains contribute to formation of a stable enzyme, and that the in vitro behavior of cloned APTX alleles can score disease-associated mutations.
 Temperature Humans Adenosine Monophosphate - chemistry Substrate Specificity RNA, Messenger - metabolism Metals - chemistry Motor Neuron Disease - genetics Apraxias - genetics Escherichia coli - metabolism Ataxia - genetics Binding Sites Protein Structure, Tertiary Zinc Fingers Mutagenesis, Site-Directed Electrophoresis, Polyacrylamide Gel Nuclear Proteins - chemistry DNA-Binding Proteins - chemistry Plasmids - metabolism Blotting, Western Syndrome Phenotype Eye Diseases - genetics Alleles Protein Binding Cations Hydrolases - chemistry DNA Damage Kinetics Mutation Lysine - chemistry Hydrogen-Ion Concentration

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