1qsl
From Proteopedia
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'''KLENOW FRAGMENT COMPLEXED WITH SINGLE-STRANDED SUBSTRATE AND EUROPIUM (III) ION''' | '''KLENOW FRAGMENT COMPLEXED WITH SINGLE-STRANDED SUBSTRATE AND EUROPIUM (III) ION''' | ||
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[[Category: Brautigam, C A.]] | [[Category: Brautigam, C A.]] | ||
[[Category: Steitz, T A.]] | [[Category: Steitz, T A.]] | ||
| - | [[Category: | + | [[Category: Exonuclease]] |
| - | [[Category: | + | [[Category: Single-stranded dna]] |
| - | [[Category: | + | [[Category: Transferase/dna]] |
| - | [[Category: | + | [[Category: Two metal ion]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 06:39:28 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 03:39, 3 May 2008
KLENOW FRAGMENT COMPLEXED WITH SINGLE-STRANDED SUBSTRATE AND EUROPIUM (III) ION
Overview
BACKGROUND: Biochemical and biophysical experiments have shown that two catalytically essential divalent metal ions (termed 'A' and 'B') bind to the 3'-5' exonuclease active site of the Klenow fragment (KF) of Escherichia coli DNA polymerase I. X-ray crystallographic studies have established the normal positions in the KF 3'-5' exonuclease (KF exo) active site of the two cations and the single-stranded DNA substrate. Lanthanide (III) luminescence studies have demonstrated, however, that only a single europium (III) ion (Eu3+) binds to the KF exo active site. Furthermore, Eu3+ does not support catalysis by KF exo or several other two-metal-ion phosphoryl-transfer enzymes. RESULTS: A crystal structure of KF complexed with both Eu3+ and substrate single-stranded oligodeoxynucleotide shows that a lone Eu3+ is bound near to metal-ion site A. Comparison of this structure to a relevant native structure reveals that the bound Eu3+ causes a number of changes to the KF exo active site. The scissile phosphate of the substrate is displaced from its normal position by about 1 A when Eu3+ is bound and the presence of Eu3+ in the active site precludes the binding of the essential metal ion B. CONCLUSIONS: The substantial, lanthanide-induced differences in metal-ion and substrate binding to KF exo account for the inhibition of this enzyme by Eu3+. These changes also explain the inability of KF exo to bind more than one cation in the presence of lanthanides. The mechanistic similarity between KF exo and other two-metal-ion phosphoryl-transfer enzymes suggests that the principles of lanthanide (III) ion binding and inhibition ascertained from this study will probably apply to most members of this class of enzymes.
About this Structure
1QSL is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Structural elucidation of the binding and inhibitory properties of lanthanide (III) ions at the 3'-5' exonucleolytic active site of the Klenow fragment., Brautigam CA, Aschheim K, Steitz TA, Chem Biol. 1999 Dec;6(12):901-8. PMID:10631518 Page seeded by OCA on Sat May 3 06:39:28 2008
