1e9n
From Proteopedia
| Line 6: | Line 6: | ||
==Overview== | ==Overview== | ||
The major human abasic endonuclease, Ape1, is an essential DNA repair, enzyme that initiates the removal of apurinic/apyrimidinic sites from DNA, excises 3' replication-blocking moieties, and modulates the DNA binding, activity of several transcriptional regulators. We have determined the, X-ray structure of the full-length human Ape1 enzyme in two new crystal, forms, one at neutral and one at acidic pH. The new structures are, generally similar to the previously determined structure of a truncated, Ape1 protein, but differ in the conformation of several loop regions and, in spans of residues with weak electron density. While only one, active-site metal ion is present in the structure determined at low pH, the structure determined from a crystal grown at the pH optimum of Ape1, nuclease activity, pH 7.5, has two metal ions bound 5 A apart in the, active site. Enzyme kinetic data indicate that at least two metal-binding, sites are functionally important, since Ca(2+) exhibits complex, stimulatory and inhibitory effects on the Mg(2+)-dependent catalysis of, Ape1, even though Ca(2+) itself does not serve as a cofactor. In, conjunction, the structural and kinetic data suggest that Ape1 catalyzes, hydrolysis of the DNA backbone through a two metal ion-mediated mechanism. | The major human abasic endonuclease, Ape1, is an essential DNA repair, enzyme that initiates the removal of apurinic/apyrimidinic sites from DNA, excises 3' replication-blocking moieties, and modulates the DNA binding, activity of several transcriptional regulators. We have determined the, X-ray structure of the full-length human Ape1 enzyme in two new crystal, forms, one at neutral and one at acidic pH. The new structures are, generally similar to the previously determined structure of a truncated, Ape1 protein, but differ in the conformation of several loop regions and, in spans of residues with weak electron density. While only one, active-site metal ion is present in the structure determined at low pH, the structure determined from a crystal grown at the pH optimum of Ape1, nuclease activity, pH 7.5, has two metal ions bound 5 A apart in the, active site. Enzyme kinetic data indicate that at least two metal-binding, sites are functionally important, since Ca(2+) exhibits complex, stimulatory and inhibitory effects on the Mg(2+)-dependent catalysis of, Ape1, even though Ca(2+) itself does not serve as a cofactor. In, conjunction, the structural and kinetic data suggest that Ape1 catalyzes, hydrolysis of the DNA backbone through a two metal ion-mediated mechanism. | ||
| + | |||
| + | ==Disease== | ||
| + | Known diseases associated with this structure: Autoimmune polyglandular disease, type I OMIM:[[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=607358 607358]], Sveinsson choreoretinal atrophy OMIM:[[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=189967 189967]] | ||
==About this Structure== | ==About this Structure== | ||
| Line 28: | Line 31: | ||
[[Category: ref-1]] | [[Category: ref-1]] | ||
| - | ''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov | + | ''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov 12 16:41:29 2007'' |
Revision as of 14:35, 12 November 2007
|
A SECOND DIVALENT METAL ION IN THE ACTIVE SITE OF A NEW CRYSTAL FORM OF HUMAN APURINIC/APYRIMIDINIC ENDONUCLEASE, APE1, AND ITS IMPLICATIONS FOR THE CATALYTIC MECHANISM
Contents |
Overview
The major human abasic endonuclease, Ape1, is an essential DNA repair, enzyme that initiates the removal of apurinic/apyrimidinic sites from DNA, excises 3' replication-blocking moieties, and modulates the DNA binding, activity of several transcriptional regulators. We have determined the, X-ray structure of the full-length human Ape1 enzyme in two new crystal, forms, one at neutral and one at acidic pH. The new structures are, generally similar to the previously determined structure of a truncated, Ape1 protein, but differ in the conformation of several loop regions and, in spans of residues with weak electron density. While only one, active-site metal ion is present in the structure determined at low pH, the structure determined from a crystal grown at the pH optimum of Ape1, nuclease activity, pH 7.5, has two metal ions bound 5 A apart in the, active site. Enzyme kinetic data indicate that at least two metal-binding, sites are functionally important, since Ca(2+) exhibits complex, stimulatory and inhibitory effects on the Mg(2+)-dependent catalysis of, Ape1, even though Ca(2+) itself does not serve as a cofactor. In, conjunction, the structural and kinetic data suggest that Ape1 catalyzes, hydrolysis of the DNA backbone through a two metal ion-mediated mechanism.
Disease
Known diseases associated with this structure: Autoimmune polyglandular disease, type I OMIM:[607358], Sveinsson choreoretinal atrophy OMIM:[189967]
About this Structure
1E9N is a Single protein structure of sequence from Homo sapiens with PB as ligand. Active as DNA-(apurinic or apyrimidinic site) lyase, with EC number 4.2.99.18 Structure known Active Sites: PB1, PB2, PB3 and PB4. Full crystallographic information is available from OCA.
Reference
Two divalent metal ions in the active site of a new crystal form of human apurinic/apyrimidinic endonuclease, Ape1: implications for the catalytic mechanism., Beernink PT, Segelke BW, Hadi MZ, Erzberger JP, Wilson DM 3rd, Rupp B, J Mol Biol. 2001 Apr 6;307(4):1023-34. PMID:11286553
Page seeded by OCA on Mon Nov 12 16:41:29 2007
