1OB8

Holliday Junction Resolving Enzyme

Summary for 1OB8

• Entry DOI: 10.2210/pdb1ob8/pdb
• Related: 1OB9
• Descriptor: HOLLIDAY-JUNCTION RESOLVASE, SULFATE ION, 1,2-ETHANEDIOL, ... (4 entities in total)
• Functional Keywords: hydrolase, enzyme, homologous recombination, holliday junction resolving enzyme, nuclease, archaea, thermophile
• Biological source: SULFOLOBUS SOLFATARICUS
• Total number of polymer chains: 2
• Total formula weight: 31712.79

Authors

Middleton, C.L.,Parker, J.L.,Richard, D.J.,White, M.F.,Bond, C.S. (deposition date: 2003-01-28, release date: 2004-10-15, Last modification date: 2024-05-01)

Primary citation

Middleton, C.L.,Parker, J.L.,Richard, D.J.,White, M.F.,Bond, C.S.
Substrate Recognition and Catalysis by the Holliday Junction Resolving Enzyme Hje.
Nucleic Acids Res., 32:5442-, 2004

PubMed Abstract: 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.

PubMed: 15479781
DOI: 10.1093/NAR/GKH869

Experimental method

X-RAY DIFFRACTION (1.8 Å)