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| {{STRUCTURE_1ob8| PDB=1ob8 | SCENE= }} | | {{STRUCTURE_1ob8| PDB=1ob8 | SCENE= }} |
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| '''HOLLIDAY JUNCTION RESOLVING ENZYME'''
| | ===HOLLIDAY JUNCTION RESOLVING ENZYME=== |
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| ==Overview==
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| Two archaeal Holliday junction resolving enzymes, Holliday junction cleavage (Hjc) and Holliday junction endonuclease (Hje), have been characterized. Both are members of a nuclease superfamily that includes the type II restriction enzymes, although their DNA cleaving activity is highly specific for four-way junction structure and not nucleic acid sequence. Despite 28% sequence identity, Hje and Hjc cleave junctions with distinct cutting patterns--they cut different strands of a four-way junction, at different distances from the junction centre. We report the high-resolution crystal structure of Hje from Sulfolobus solfataricus. The structure provides a basis to explain the differences in substrate specificity of Hje and Hjc, which result from changes in dimer organization, and suggests a viral origin for the Hje gene. Structural and biochemical data support the modelling of an Hje:DNA junction complex, highlighting a flexible loop that interacts intimately with the junction centre. A highly conserved serine residue on this loop is shown to be essential for the enzyme's activity, suggesting a novel variation of the nuclease active site. The loop may act as a conformational switch, ensuring that the active site is completed only on binding a four-way junction, thus explaining the exquisite specificity of these enzymes.
| | The line below this paragraph, {{ABSTRACT_PUBMED_15479781}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 15479781 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_15479781}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Nuclease]] | | [[Category: Nuclease]] |
| [[Category: Thermophile]] | | [[Category: Thermophile]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 03:37:21 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 23:05:12 2008'' |
