1ob8
From Proteopedia
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HOLLIDAY JUNCTION RESOLVING ENZYME
Overview
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.
About this Structure
1OB8 is a Single protein structure of sequence from Sulfolobus solfataricus with SO4 and EDO as ligands. Structure known Active Site: SA1. Full crystallographic information is available from OCA.
Reference
Substrate recognition and catalysis by the Holliday junction resolving enzyme Hje., Middleton CL, Parker JL, Richard DJ, White MF, Bond CS, Nucleic Acids Res. 2004 Oct 12;32(18):5442-51. Print 2004. PMID:15479781
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