1ipi
From Proteopedia
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CRYSTAL STRUCTURE OF THE ARCHAEAL HOLLIDAY JUNCTION RESOLVASE HJC FROM PYROCOCCUS FURIOSUS FORM II
Overview
Hjc is an archaeal DNA endonuclease, which resolves the Holliday junction, in the presence of divalent metals. Combined with mutational analyses, the, x-ray structure of the Pyrococcus furiosus Hjc crystal grown in the, presence of ammonium sulfate revealed a positively charged interface, rich, in conserved basic residues, and the catalytic center (Nishino, T., Komori, K., Tsuchiya, D., Ishino, Y., and Morikawa, K. (2001) Structure 9, 197-T204). This structural study also suggested that the N-terminal, segment and some loops of Hjc play crucial roles in the cleavage of DNA., However, a structural view of the interaction between these regions and, DNA remains elusive. To clarify the regional roles of Hjc in the, recognition of the Holliday junction, further structural and biochemical, analyses were carried out. A new crystal form of Hjc was obtained from a, polyethylene glycol solution in the absence of ammonium sulfate, and its, structure has been determined at 2.16-A resolution. A comparison of the, two crystal structures has revealed that the N-terminal segment undergoes, a serious conformational change. The site-directed mutagenesis of the, sulfate-binding site within the segment caused a dramatic decrease in the, junction binding, but the mutant was still capable of cleaving DNA with a, 20-fold lower efficiency. The kinetic analysis of Hjc-Holliday junction, interaction indicated that mutations in the N-terminal segment greatly, increased the dissociation rate constants of the Hjc-Holliday junction, complex, explaining the decreased stability of the complex. This segment, is also responsible for the disruption of base pairs near the junction, center, through specific interactions with them. Taken together, these, results imply that, in addition to the secondary effects of two basic, loops, the flexible N-terminal segment plays predominant roles in the, recognition of DNA conformation near the crossover and in correct, positioning of the cleavage site to the catalytic center of the Hjc, resolvase.
About this Structure
1IPI is a Single protein structure of sequence from Pyrococcus furiosus. Active as Crossover junction endodeoxyribonuclease, with EC number 3.1.22.4 Full crystallographic information is available from OCA.
Reference
Dissection of the regional roles of the archaeal Holliday junction resolvase Hjc by structural and mutational analyses., Nishino T, Komori K, Ishino Y, Morikawa K, J Biol Chem. 2001 Sep 21;276(38):35735-40. Epub 2001 Jul 5. PMID:11441015
Page seeded by OCA on Sat Nov 24 22:20:38 2007
