Abstract
Inositol polyphosphate 5-phosphatases are central to intracellular processes ranging from membrane trafficking to Ca(2+) signaling, and defects in this activity result in the human disease Lowe syndrome. The 1.8 resolution structure of the inositol polyphosphate 5-phosphatase domain of SPsynaptojanin bound to Ca(2+) and inositol (1,4)-bisphosphate reveals a fold and an active site His and Asp pair resembling those of several Mg(2+)-dependent nucleases. Additional loops mediate specific inositol polyphosphate contacts. The 4-phosphate of inositol (1,4)-bisphosphate is misoriented by 4.6 compared to the reactive geometry observed in the apurinic/apyrimidinic endonuclease 1, explaining the dephosphorylation site selectivity of the 5-phosphatases. Based on the structure, a series of mutants are described that exhibit altered substrate specificity providing general determinants for substrate recognition.
MeSH terms
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Amino Acid Sequence
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Binding Sites
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Calcium / metabolism
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Catalytic Domain
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Cloning, Molecular
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Crystallography, X-Ray
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Enzyme Inhibitors / metabolism
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Humans
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Inositol Phosphates / metabolism
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Inositol Polyphosphate 5-Phosphatases
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Models, Molecular
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Molecular Sequence Data
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Mutation
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Nerve Tissue Proteins / chemistry*
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Nerve Tissue Proteins / genetics
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Nerve Tissue Proteins / metabolism
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Phosphoric Monoester Hydrolases / chemistry*
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Phosphoric Monoester Hydrolases / genetics
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Phosphoric Monoester Hydrolases / metabolism
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Phosphorylation
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Protein Conformation
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Protein Folding
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Protein Structure, Quaternary
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Protein Structure, Secondary
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Protein Structure, Tertiary
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Schizosaccharomyces / enzymology
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Schizosaccharomyces / genetics
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Sequence Alignment
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Substrate Specificity
Substances
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Enzyme Inhibitors
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Inositol Phosphates
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Nerve Tissue Proteins
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Recombinant Proteins
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inositol 1,4-bis(phosphate)
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synaptojanin
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Phosphoric Monoester Hydrolases
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Inositol Polyphosphate 5-Phosphatases
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Calcium