2ihn
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(New page: 200px<br /><applet load="2ihn" size="450" color="white" frame="true" align="right" spinBox="true" caption="2ihn, resolution 3.00Å" /> '''Co-crystal of Bacter...)
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Revision as of 10:12, 21 November 2007
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Co-crystal of Bacteriophage T4 RNase H with a fork DNA substrate
Overview
Bacteriophage T4 RNase H, a flap endonuclease-1 family nuclease, removes, RNA primers from lagging strand fragments. It has both 5 nuclease and flap, endonuclease activities. Our previous structure of native T4 RNase H (PDB, 1TFR) revealed an active site composed of highly conserved Asp residues, and two bound hydrated magnesium ions. Here, we report the crystal, structure of T4 RNase H in complex with a fork DNA substrate bound in its, active site. This is the first structure of a FEN-1 family protein with, its complete branched substrate. The fork duplex interacts with an, extended loop of the HhH2 motif. The 5 arm crosses over the active site, extending below the bridge (helical arch) region. Cleavage assays of this, DNA substrate identify a primary cut site 7-bases in from the 5 arm. The, scissile phosphate, the first bond in the duplex DNA adjacent to the 5, arm, lies above a magnesium binding site. The less ordered 3 arm reaches, towards the C- and N- termini of the enzyme, which are binding sites for, T4 32 protein and T4 45 clamp, respectively. In the crystal structure, the, scissile bond is located within the double-stranded DNA, between the first, two duplex nucleotides next to the 5 arm, and lies above a magnesium, binding site. This complex provides important insight into substrate, recognition and specificity of the FEN-1 enzymes.
About this Structure
2IHN is a Single protein structure of sequence from Bacteriophage t4. Active as Ribonuclease H, with EC number 3.1.26.4 Full crystallographic information is available from OCA.
Reference
Crystal structure of bacteriophage T4 5' nuclease in complex with a branched DNA reveals how FEN-1 family nucleases bind their substrates., Devos JM, Tomanicek SJ, Jones CE, Nossal NG, Mueser TC, J Biol Chem. 2007 Aug 9;. PMID:17693399
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