Substrate recognition and catalysis by the Holliday junction resolving enzyme Hje

Middleton, Claire L., Parker, Joanne L., Richard, Derek J., White, Malcolm F., & Bond, Charles S. (2004) Substrate recognition and catalysis by the Holliday junction resolving enzyme Hje. Nucleic Acids Research, 32(18), pp. 5442-5451.

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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.

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ID Code: 40629
Item Type: Journal Article
Refereed: Yes
Additional Information: Articles free to read on journal website
Keywords: Holliday junction cleavage, enzymes, Holliday junction endonuclease
DOI: 10.1093/nar/gkh869
ISSN: 1362-4962
Divisions: Past > QUT Faculties & Divisions > Faculty of Science and Technology
Copyright Owner: Copyright 2004 Oxford Journals
Copyright Statement: This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (
by-nc/2.5), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Deposited On: 09 Mar 2011 22:59
Last Modified: 29 Jan 2015 01:38

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