1e3c: Difference between revisions
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==Overview== | ==Overview== | ||
Arylsulfatase A (ASA) belongs to the sulfatase family whose members carry | Arylsulfatase A (ASA) belongs to the sulfatase family whose members carry a C(alpha)-formylglycine that is post-translationally generated by oxidation of a conserved cysteine or serine residue. The crystal structures of two arylsulfatases, ASA and ASB, and kinetic studies on ASA mutants led to different proposals for the catalytic mechanism in the hydrolysis of sulfate esters.The structures of two ASA mutants that lack the functional C(alpha)-formylglycine residue 69, in complex with a synthetic substrate, have been determined in order to unravel the reaction mechanism. The crystal structure of the inactive mutant C69A-ASA in complex with p-nitrocatechol sulfate (pNCS) mimics a reaction intermediate during sulfate ester hydrolysis by the active enzyme, without the covalent bond to the key side-chain FGly69. The structure shows that the side-chains of lysine 123, lysine 302, serine 150, histidine 229, the main-chain of the key residue 69 and the divalent cation in the active center are involved in sulfate binding. It is proposed that histidine 229 protonates the leaving alcoholate after hydrolysis.C69S-ASA is able to bind covalently to the substrate and hydrolyze it, but is unable to release the resulting sulfate. Nevertheless, the resulting sulfation is low. The structure of C69S-ASA shows the serine side-chain in a single conformation, turned away from the position a substrate occupies in the complex. This suggests that the double conformation observed in the structure of wild-type ASA is more likely to correspond to a formylglycine hydrate than to a twofold disordered aldehyde oxo group, and accounts for the relative inertness of the C69S-ASA mutant. In the C69S-ASA-pNCS complex, the substrate occupies the same position as in the C69A-ASA-pNCS complex, which corresponds to the non-covalently bonded substrate. Based on the structural data, a detailed mechanism for sulfate ester cleavage is proposed, involving an aldehyde hydrate as the functional group. | ||
==Disease== | ==Disease== | ||
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[[Category: Homo sapiens]] | [[Category: Homo sapiens]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Buelow, R | [[Category: Buelow, R Von.]] | ||
[[Category: Dierks, T.]] | [[Category: Dierks, T.]] | ||
[[Category: Figura, K | [[Category: Figura, K Von.]] | ||
[[Category: Schmidt, B.]] | [[Category: Schmidt, B.]] | ||
[[Category: Uson, I.]] | [[Category: Uson, I.]] | ||
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[[Category: lysosomal enzyme]] | [[Category: lysosomal enzyme]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:23:19 2008'' | ||
Revision as of 13:23, 21 February 2008
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CRYSTAL STRUCTURE OF AN ARYLSULFATASE A MUTANT C69S SOAKED IN SYNTHETIC SUBSTRATE
OverviewOverview
Arylsulfatase A (ASA) belongs to the sulfatase family whose members carry a C(alpha)-formylglycine that is post-translationally generated by oxidation of a conserved cysteine or serine residue. The crystal structures of two arylsulfatases, ASA and ASB, and kinetic studies on ASA mutants led to different proposals for the catalytic mechanism in the hydrolysis of sulfate esters.The structures of two ASA mutants that lack the functional C(alpha)-formylglycine residue 69, in complex with a synthetic substrate, have been determined in order to unravel the reaction mechanism. The crystal structure of the inactive mutant C69A-ASA in complex with p-nitrocatechol sulfate (pNCS) mimics a reaction intermediate during sulfate ester hydrolysis by the active enzyme, without the covalent bond to the key side-chain FGly69. The structure shows that the side-chains of lysine 123, lysine 302, serine 150, histidine 229, the main-chain of the key residue 69 and the divalent cation in the active center are involved in sulfate binding. It is proposed that histidine 229 protonates the leaving alcoholate after hydrolysis.C69S-ASA is able to bind covalently to the substrate and hydrolyze it, but is unable to release the resulting sulfate. Nevertheless, the resulting sulfation is low. The structure of C69S-ASA shows the serine side-chain in a single conformation, turned away from the position a substrate occupies in the complex. This suggests that the double conformation observed in the structure of wild-type ASA is more likely to correspond to a formylglycine hydrate than to a twofold disordered aldehyde oxo group, and accounts for the relative inertness of the C69S-ASA mutant. In the C69S-ASA-pNCS complex, the substrate occupies the same position as in the C69A-ASA-pNCS complex, which corresponds to the non-covalently bonded substrate. Based on the structural data, a detailed mechanism for sulfate ester cleavage is proposed, involving an aldehyde hydrate as the functional group.
DiseaseDisease
Known disease associated with this structure: Metachromatic leukodystrophy OMIM:[607574]
About this StructureAbout this Structure
1E3C is a Single protein structure of sequence from Homo sapiens with as ligand. Active as Cerebroside-sulfatase, with EC number 3.1.6.8 Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of an enzyme-substrate complex provides insight into the interaction between human arylsulfatase A and its substrates during catalysis., von Bulow R, Schmidt B, Dierks T, von Figura K, Uson I, J Mol Biol. 2001 Jan 12;305(2):269-77. PMID:11124905
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