1ej9
From Proteopedia
(New page: 200px<br /> <applet load="1ej9" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ej9, resolution 2.6Å" /> '''CRYSTAL STRUCTURE OF...) |
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caption="1ej9, resolution 2.6Å" /> | caption="1ej9, resolution 2.6Å" /> | ||
'''CRYSTAL STRUCTURE OF HUMAN TOPOISOMERASE I DNA COMPLEX'''<br /> | '''CRYSTAL STRUCTURE OF HUMAN TOPOISOMERASE I DNA COMPLEX'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Human topoisomerase I helps to control the level of DNA supercoiling in | + | Human topoisomerase I helps to control the level of DNA supercoiling in cells and is vital for numerous DNA metabolic events, including replication, transcription, and recombination. The 2.6 A crystal structure of human topoisomerase I in noncovalent complex with a DNA duplex containing a cytosine at the -1 position of the scissile strand rather than the favored thymine is reported. The hydrogen bond between the O2 position of this -1 base and the epsilon-amino of the conserved Lys-532 residue, the only base-specific contact observed previously in the human topoisomerase I-DNA interaction, is maintained in this complex. Several unique features of this structure, however, have implications for the DNA-binding and active-site mechanisms of the enzyme. First, the ends of the DNA duplex were observed to shift by up to 5.4 A perpendicular to the DNA helical axis relative to structures reported previously, suggesting a novel degree of plasticity in the interaction between human topoisomerase I and its DNA substrate. Second, 12 additional residues at the NH(2) terminus of the protein (Trp-203-Gly-214) could be built in this structure, and they were found to pack against the putative hinge region implicated in the clamping of the enzyme around duplex DNA. Third, a water molecule was observed adjacent to the scissile phosphate and the active-site residues; the potential specific base character of this solvent molecule in the active-site mechanism of the enzyme is discussed. Fourth, the scissile phosphate group was found to be rotated by 75 degrees, bringing Lys-532 into hydrogen-bonding distance of one of the nonbridging phosphate oxygens. This orientation of the scissile phosphate group implicates Lys-532 as a fifth active-site residue, and also mimics the orientation observed for the 3'-phosphotyrosine linkage in the covalent human topoisomerase I-DNA complex structure. The implications of these structural features for the mechanism of the enzyme are discussed, including the potential requirement for a rotation of the scissile phosphate group during DNA strand cleavage and covalent attachment. |
==Disease== | ==Disease== | ||
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==About this Structure== | ==About this Structure== | ||
| - | 1EJ9 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Active as [http://en.wikipedia.org/wiki/DNA_topoisomerase DNA topoisomerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.99.1.2 5.99.1.2] Full crystallographic information is available from [http:// | + | 1EJ9 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Active as [http://en.wikipedia.org/wiki/DNA_topoisomerase DNA topoisomerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.99.1.2 5.99.1.2] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1EJ9 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Homo sapiens]] | [[Category: Homo sapiens]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Champoux, J | + | [[Category: Champoux, J J.]] |
| - | [[Category: Hol, W | + | [[Category: Hol, W G.]] |
| - | [[Category: Redinbo, M | + | [[Category: Redinbo, M R.]] |
[[Category: human]] | [[Category: human]] | ||
[[Category: protein-dna complex]] | [[Category: protein-dna complex]] | ||
[[Category: type i topoisomerase]] | [[Category: type i topoisomerase]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:28:20 2008'' |
Revision as of 10:28, 21 February 2008
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CRYSTAL STRUCTURE OF HUMAN TOPOISOMERASE I DNA COMPLEX
Contents |
Overview
Human topoisomerase I helps to control the level of DNA supercoiling in cells and is vital for numerous DNA metabolic events, including replication, transcription, and recombination. The 2.6 A crystal structure of human topoisomerase I in noncovalent complex with a DNA duplex containing a cytosine at the -1 position of the scissile strand rather than the favored thymine is reported. The hydrogen bond between the O2 position of this -1 base and the epsilon-amino of the conserved Lys-532 residue, the only base-specific contact observed previously in the human topoisomerase I-DNA interaction, is maintained in this complex. Several unique features of this structure, however, have implications for the DNA-binding and active-site mechanisms of the enzyme. First, the ends of the DNA duplex were observed to shift by up to 5.4 A perpendicular to the DNA helical axis relative to structures reported previously, suggesting a novel degree of plasticity in the interaction between human topoisomerase I and its DNA substrate. Second, 12 additional residues at the NH(2) terminus of the protein (Trp-203-Gly-214) could be built in this structure, and they were found to pack against the putative hinge region implicated in the clamping of the enzyme around duplex DNA. Third, a water molecule was observed adjacent to the scissile phosphate and the active-site residues; the potential specific base character of this solvent molecule in the active-site mechanism of the enzyme is discussed. Fourth, the scissile phosphate group was found to be rotated by 75 degrees, bringing Lys-532 into hydrogen-bonding distance of one of the nonbridging phosphate oxygens. This orientation of the scissile phosphate group implicates Lys-532 as a fifth active-site residue, and also mimics the orientation observed for the 3'-phosphotyrosine linkage in the covalent human topoisomerase I-DNA complex structure. The implications of these structural features for the mechanism of the enzyme are discussed, including the potential requirement for a rotation of the scissile phosphate group during DNA strand cleavage and covalent attachment.
Disease
Known disease associated with this structure: DNA topoisomerase I, camptothecin-resistant OMIM:[126420]
About this Structure
1EJ9 is a Single protein structure of sequence from Homo sapiens. Active as DNA topoisomerase, with EC number 5.99.1.2 Full crystallographic information is available from OCA.
Reference
Novel insights into catalytic mechanism from a crystal structure of human topoisomerase I in complex with DNA., Redinbo MR, Champoux JJ, Hol WG, Biochemistry. 2000 Jun 13;39(23):6832-40. PMID:10841763
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